Certain Big, Charged Molecules Are Universal to Life on Earth. Can They Help Detect It In The Far Solar System?

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This article of mine, slightly tweaked for Many Worlds, first appeared today (July 6)  in Astrobiology Magazine,  www.astrobio.net

NASA’s Cassini spacecraft completed its deepest-ever dive through the icy plume of Enceladus on Oct. 28, 2015. The spacecraft did not have instruments that could detect life, but missions competing for NASA New Frontiers funding will — raising the thorny question of how life might be detected. (NASA/JPL-Caltech)

As NASA inches closer to launching new missions to the Solar System’s outer moons in search of life, scientists are renewing their focus on developing a set of universal characteristics of life that can be measured.

There is much debate about what might be considered a clear sign of life, in part, because there are so many definitions separating the animate from the inanimate.

NASA’s prospective missions to promising spots on Europa, Enceladus and Titan have their individual approaches to detecting life, but one respected voice in the field says there is a better way that’s far less prone to false positives.

Noted chemist and astrobiologist Steven Benner says life’s signature is not necessarily found in the presence of particular elements and compounds, nor in its effects on the surrounding environment, and is certainly not something visible to the naked eye (or even a sophisticated camera).

Rather, life can be viewed as a structure, a molecular backbone that Benner and his group, Foundation for Applied Molecular Evolution (FfAME), have identified as the common inheritance of all living things. Its central function is to enable what origin-of-life scientists generally see as an essential dynamic in the onset of life and its increased complexity and spread: Darwinian evolution via transfer of information, mutation and the transfer of those mutations.

“What we’re looking for is a universal molecular bio-signature, and it does exist in water,” says Benner. “You want a genetic molecule that can change physical conditions without changing physical properties — like DNA and RNA can do.”

Steven Benner, director of the Foundation for Applied Molecular Evolution or FfAME. (SETI)

Looking for DNA or RNA on an icy moon, or elsewhere would presuppose life like our own — and life that has already done quite a bit of evolving.

A more general approach is to find a linear polymer (a large molecule, or macromolecule, composed of many repeated subunits, of which DNA and RNA are types) with an electrical charge. That, he said, is a structure that is universal to life, and it can be detected.

As described in a recent paper that Benner’s group published in the journal Astrobiology: “the only molecular systems able to support Darwinian information are linear polymers that have a repeating backbone charge. These are called ‘polyelectrolytes.’

“These data suggest that polyelectrolytes will be the genetic molecules in all life, no matter what its origin and no matter what the direction or tempo of its natural history, as long as it lives in water.”

Through years of experimentation, Benner and others have found that electric charges in these crucial polymers, or “backbones,” of life have to repeat. If they are a mixture of positive and negative charges, then the ability to pass on changing information without the structure itself changing is lost.

And as a result, Benner says, detecting these charged, linear and repeating large molecules is potentially quite possible on Europa or Enceladus or wherever water is found. All you have to do is expose those charged and repeating molecular structures to an instrument with the opposite charge and measure the reaction.

Polyelectrolytes are long-chain, molecular semiconductors, whose backbones contain electrons. The structure and composition of the polyelectrolytes confers an ability to transfer electric charge and the energy of electronic excited states over distance. (Azyner Group, UCSC)

James Green, director of NASA’s Planetary Sciences division, sees values in this approach.

“Benner’s polyelectrolyte study is fascinating to me since it provides our scientists another critical discussion point about finding life with some small number of experiments,” he says.

“Finding life is very high bar to cross; it has to metabolize, reproduce, and evolve — all of which I can’t develop an experiment to measure on another planet or moon. If it doesn’t talk or move in front of the camera we are left with developing a very challenging set of instruments that can only measure attributes. So polyelectrolytes are one more to consider.”

Benner has been describing his universal molecular bio-signature to leaders of the groups competing for New Frontiers missions, which fill the gap between smaller Discovery missions and large flagship planetary missions. It’s taken a while but due to his efforts over several years, he notes that interest seems to be growing in incorporating his findings.

Astrobiologist Chris McKay at NASA’s Ames Research Center.  (IDG News Service)

In particular, Chris McKay, a prominent astrobiologist at NASA’s Ames Research Center and a member of one of the New Frontiers Enceladus proposal teams, says he thinks there is merit to Benner’s idea.

“The really interesting aspect of this suggestion is that new technologies are now available for sequencing DNA that can be generalized to read any linear molecule,” McKay writes in an email.

In other words, they can detect any polyelectrolytes.

Other teams are confident that their own kinds of life detection instruments can do the job. Morgan Cable, deputy project scientist of the Enceladus Life Finder proposal, she says her team has great confidence in its four-pronged approach.   A motto of the mission on some of its written material is: “If Encedadus has life, we will find it.”

Morgan Cable, deputy project scientist for the proposed Enceladus Life Finder.

The package includes instruments like mass spectrometers able to detect large molecules associated with life; measurements of energy gradients that allow life to be nourished; detection of isotopic signatures associated with life; and identification of long carbon chains that serve as membranes to house the components of a cell.

“Not one but all four indicators have to point to life to make a potential detection,” Cable says.

NASA is winnowing down 12 proposals by late this year, so, Benner’s ideas could play a role later in the process as well. NASA’s goal is to select its next New Frontiers mission in about two years, with launch in the mid-2020s.

The Europa Clipper orbiter mission is tentatively scheduled to launch in 2022, but its companion lander has been scrubbed for now by the Trump administration.

Nonetheless, NASA put out a call last month for instruments that might one day sample the ice of Europa. Benner is once more hoping that his theory of polyelectrolytes as the key to identifying life in water or ice will be considered and embraced.

These composite images show a suspected plume of material erupting two years apart from the same location on Jupiter’s icy moon Europa. Both plumes, photographed in UV light by Hubble, were seen in silhouette as the moon passed in front of Jupiter.  Europa is a major focus of the search for life beyond Earth. (NASA/ESA/STScI/USGS)
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Planetary Protection is a “Wicked” Problem

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The Viking landers were baked for 30 hours after assembly, a dry heat sterilization that is considered the gold standard for planetary protection.  Before the baking, the landers were given a preliminary cleaning to reduce the number of potential microbial spores.  The levels achieved with that preliminary cleaning are similar to what is now required for a mission to Mars unless the destination is an area known to be suitable for Martian life.  In that case, a sterilizing equivalent to the Viking baking is required.  (NASA)

The only time that a formally designated NASA “life detection” mission was flown to another planet or moon was when the two Viking landers headed to Mars forty years ago.

The odds of finding some kind of Martian life seemed so promising at the time that there was little dispute about how much energy, money and care should be allocated to making sure the capsule would not be carrying any Earth life to the planet.  And so after the two landers had been assembled, they were baked at more than 250 °F for three days to sterilize any parts that would come into contact with Mars.

Although the two landers successfully touched down on the Martian surface and did some impressive science, the life detection portion of the mission was something of a fiasco — with conflict, controversy and ultimately quite a bit of confusion.

Clearly, scientists did not yet know enough about how to search for life beyond Earth and the confounding results pretty much eliminated life-detection from NASA’s missions for decades.

But scientific and technological advances of the last ten years have put life detection squarely back on the agenda — in terms of future searches for fossil biosignatures on Mars and for potential life surviving in the oceans of Europa and Enceladus.  What’s more, both NASA and private space companies talk seriously of sending humans to Mars in the not-too-distant future.

With so many missions being planned, developed and proposed for solar system planets and moons, the issue of planetary protection has also gained a higher profile.  It seems to have become more contentious and to some seems far less straight-forward as it used to be.

A broad consensus appears to remain that bringing Earth life to another planet or moon, especially if it is potentially habitable, is a real possibility that is both scientifically and ethically fraught. But there are rumblings about just how much time, money and attention needs to be brought to satisfying the requirements of “planetary protection.”

In fact, it has become a sufficiently significant question that the first plenary session of the recent Astrobiology Science Conference in Mesa, Arizona was dedicated to it.  The issue, which was taken up in later technical sessions as well, was how to assess and weigh the risks of bringing Earth life to other bodies versus the benefits of potentially sending out more missions, more often and more cheaply.

It is not a simple problem, explained Andrew Maynard, director of the Risk Innovation Lab at Arizona State University.  Indeed, he told the audience of scientists that it was a “wicked problem,” a broadly used terms for issues that are especially complex and involve numerous issues and players.

 

A primary barrier to keeping microbes off spacecraft and instruments going to space is to build them in clean rooms, such as this one at JPL.  These large rooms with filtered air do help lower the count of microbes on surfaces, but the bacteria are everywhere and further steps are essential.  (NASA/JPL-Caltech)

As he later elaborated to me, other “wicked” risk-benefit problems include gene editing and autonomous driving — both filled with great potential and serious potential downsides.  Like travel to other planets and moons.

“This is subjective,” Maynard said, “but I’d put planetary protection on the more wicked end of the spectrum. It combines individual priorities and ethics  — what people and groups deeply believe is right — with huge uncertainties.  That makes it something never really experienced before and so escalates all factors of wickedness.”

Those groups include scientists (who very much don’t want Mars or another potentially habitable place to be contaminated with Earth life before they can get there), to advocates of greater space exploration (who worry that planetary protection will slow or eliminate some missions they very much want to proceed), to NASA mission managers (worried about delays and costs associated with planetary protections surprises.)

And then there’s the general public which might (or might not) have entirely different ethical concerns about the potential for contaminating other planets and moons with Earth life.

No wonder the problem is deemed wicked.

We’ll get into the pros and cons, but first some background:

I asked NASA’s Planetary Protection officer, Catharine Conley, whether Earth life has been transported to its most likely solar system destination, Mars.

Her reply:  “There are definitely Earth organisms that we’ve brought to Mars and are still alive on the spacecraft.”

Catharine “Cassie” Conley has been NASA’s Planetary Protection officer since 2006. There is only one other full-time official in the world with the same responsibilities, and he works for the European Space Agency. (NASA/W. Hrybyk)

She said it is quite possible that some of those organisms were brushed off the vehicles or otherwise were shed and fell to the surface. Because of the strong ultraviolet radiation and the Earth life-destroying chemical makeup of the soil, however, it’s unlikely the organisms could last for long, and equally unlikely that any would have made it below the surface.  Nonetheless, it is sobering to hear that Earth life has already made it to Mars.

Related to this reality is the understanding that Earth life, in the form of bacteria, algae and fungi and their spores, can be extraordinarily resilient.  Organisms have been discovered that can survive unimagined extremes of heat and cold, can withstand radiation that would kill us, and can survive as dormant spores for tens of thousands of years.

What’s more, Mars scientists now know that the planet was once much warmer and wetter, and that ice underlies substantial portions of the planet. There are even signs today of seasonal runs of what some scientists argue is very briny surface water.

So the risk of Earth life surviving a ride to another planet or moon is probably greater than imagined earlier, and the possibility of that Earth life potentially surviving and spreading on a distant surface (think the oceans of Europa and Enceladus, or maybe a briny, moist hideaway on Mars) is arguably greater too.  From a planetary protection perspective, all of this is worrisome.

The logic of planetary protection is, like almost everything involved with the subject, based on probabilities.  Discussed as far back as the 1950s and formalized in the 1967 Outer Space Treaty, the standard agreed on is to take steps that ensure there is less than a 1 in 10,000 chance of a spaceship or lander or instrument from Earth bringing life to another body.

This figure takes into account the number of microorganisms on the spacecraft, the probability of growth on the planet or moon where the mission is headed, and a series of potential sanitizing to sterilizing procedures that can be used.  A formula for assessing the risk of a mission for planetary protection purposes was worked out in 1965 by Carl Sagan, along with Harvard theoretical physicist Sidney Coleman.

Deinococcus radiodurans is an extremophilic bacterium, one of the most radiation-resistant organisms known. It can survive cold, dehydration, vacuum, and acid, and is therefore known as a polyextremophile and is considered perhaps the world’s toughest bacterium. It can withstand a radiation dose 1,000 times stronger than what would kill a person.

A lot has been learned since that time, and some in the field say it’s time to re-address the basics of planetary protection.  They argue, for instance, that since we now know that Earth life can (theoretically, at least) be carried inside a meteorite from our planet to Mars, then Earth life may have long been on Mars — if it is robust enough to survive when it lands.

In addition, a great deal more is known about how to sanitize a space vehicle without baking it entirely — a step that is both very costly and could prove deadly to the more sophisticated capsules and instruments.  And more is known about the punishing environment on the surface of Mars and elsewhere.

People ranging from Mars Society founder Robert Zubrin to Cornell University Visiting Scientist Alberto G. Fairén in Nature Geoscience have argued — and sometimes railed — against planetary protection requirements. NASA mission managers have often voiced their concerns as well.  The regulations, some say, slow the pace of exploration and science to avoid a vanishingly small risk.

Brent Sherwood, planetary mission formulation manager for JPL, is currently overseeing two proposed projects for New Frontiers missions.  One is to search for signs of life on Saturn’s moon Enceladus and the other for habitability on the moon Titan. (Brent Sherwood)

Brent Sherwood, program manager for solar system mission formulation at JPL, spoke at AbSciCon about what he sees as the need for a review and possibly reassessment of the planetary protection rules and regulations.  As someone who helps scientists put together proposals for NASA missions in the solar system, he has practical and long considered views about planetary protection.

He and his co-authors argue that the broad conversation that needs to take place should include scientists, ethicists, managers, and policy makers; and especially should include the generations that will actually implement and live with the consequences of these missions.

In the abstract for his talk, Sherwood wrote:

“The (1 chance in 10,000) requirement may not be as logically sound or deserving of perpetuation as generally assumed.  What status should this requirement have within an ethical decision-making process? Do we need a meta-ethical discussion about absolute values, rather than an arbitrary number that purports to govern the absolute necessity of preserving scientific discovery or protecting alien life?”

As he  later he told me: “I’m recommending that we be proactive and engage the broadest possible range of stakeholder communities…. With these big, hairy risk problems, everything is probabilistic and open to argument.  People are bad at thinking of very small and very big numbers, and the same for risks.  They tend to substitute opinion for fact.”

Sherwood is no foe of planetary protection.  But he said planetary protection is a “foundational” part of the space program, and he wants to make sure it is properly adapted for the new space era we are entering.

Elon Musk of SpaceX, Jeff Bezos of Blue Origins and NASA have all talked about potentially sending astronauts to Mars or establishing a colony on Mars in the decades ahead.  Many obstacles remain, but planning is underway. (Bryan Versteeg/Spacehabs.com)

Planetary protection officer Conley contends that regular reviews are already built into the system.  She told me that every mission gets a thorough planetary protection assessment early in the process, and that there is no one-size-fits-all approach.  Rather, the risks and architecture of the missions are studied within the context of the prevailing rules.

In addition, she said, the group that oversees planetary protection internationally — the Committee on Space Research (COSPAR) — meets every two years and its Panel on Planetary Protection takes up general topics and welcomes input from whomever might want to raise issues large or small.

“You hear it said that there are protected areas on Mars or Europa where missions can’t go, but that’s not the case,” she said.  “These are sensitive areas where life just might be present now or was present in the past.  If that’s the case, then the capsule or lander or rover has to be sterilized to the level of the Viking missions.”

She said that she understood that today’s spacecraft are different from Viking, which was designed and built from scratch with planetary protection in mind.  Today, JPL and other mission builders get some of their parts “off the shelf” in an effort to make space exploration less expensive.

“We do have to balance the goals of exploration and space science with making sure that Earth life does not take hold.  We also have to be aware that taxpayer money is being spent.  But if a mission sent out returns a signal of life, what have we achieved if it turns out to be life we brought there?

“I see planetary protection as a great success story.  People identified a potential contamination problem back in the ’50s, put regulations into place, and have succeeded in avoiding the problem.  This kind of global cooperation that leads to the preventing of a potentially major problem just doesn’t happen that often.”

The global cooperation has been robust, Conley said, despite the fact that only NASA and the European Space Agency have a full-time planetary protection officer.  She cited the planning for the joint Russian-Chinese mission to the Martian moon Phobos as an example of other nations agreeing to very high standards.  She and her European Space Agency (ESA) counterpart traveled twice to Moscow to discuss planetary protection steps being taken.

Andrew Maynard is the director of Arizona State University’s Risk Innovation Lab and is a professor in School for the Future of Innovation in Society.  (ASU.)

So far, she said private space companies have been attentive to planetary protection as well.  Some of the commercial space activity in the future involves efforts to mine on asteroids, and Conley said there is no planetary protection issues involved.  The same with mining on our moon.

But should the day arrive that private companies such as SpaceX and Blue Origin seriously propose a human mission to Mars — as they have said they plan to — Conley said they would have the same obligations as any NASA mission.  The US has not yet determined how to ensure that compliance, she said, but companies already would need Federal Aviation Administration approval for a launch, and planetary protection is part of that.

Risk innovation expert Maynard, however, was not so sure about those protections.  He said he could imagine a situation where Elon Musk of SpaceX or Jeff Bezos of Blue Origin or any other space entrepreneur around the world would decide to move their launch to a nation that would be willing to provide the service without intensive planetary protection oversight.

“The risk of this may be small, but this is all about the potentially outsize consequences of small risks,” he said.

Maynard said that was hardly a likely scenario — and that commercial space pioneers so far have been supportive of planetary protection guidelines — but that he was well aware of the displeasure among some mission managers and participating scientists about planetary protection requirements.

Given all this, it’s easy to see how and why planetary protection advocates might feel that the floodgates are being tested, and why space explorers looking forward to a time when Mars and other bodies might be visited by astronauts and later potentially colonized are concerned about potential obstacles to their visions.

An artist’s rendering of a sample return from Mars.  Both the 2020 NASA Mars mission and the ESA-Russian mission are designed to identify and cache intriguing rocks for delivery to Earth in the years ahead. (Wickman Spacecraft & Propulsion)

This column has addressed the issue of “forward contamination” — how to prevent Earth life from being carried to another potentially habitable solar system body and surviving there.  But there is another planetary protection worry and that involves “backward contamination” — how to handle the return of potentially living extraterrestrial organisms to Earth.

That will be the subject of a later column, but suffice it to say it is very much on the global space agenda, too.

The Apollo astronauts famously brought back pounds of moon rocks, and grains of asteroid and comet dust have also been retrieved and delivered.  A sample return mission by the Russian and Chinese space agencies was designed to return rock or grain samples from the Martian moon Phobos earlier this decade, but the spacecraft did not make it beyond low Earth orbit.

However, the future will see many more sample return attempts.  The Japanese space agency JAXA launched a mission to the asteroid 162173 Ryugu in 2014 (Hayabusa 2) and it will arrive there next year.  The plan is to collect rock and dust samples and bring them back to Earth.  NASA’s OSIRIS-REx is also making its way to an asteroid, 101955 Bennu, with the goal of collecting a sample as well for return to Earth.

And in 2020 both NASA and ESA (with Russian collaboration) will launch spacecraft for Mars with the intention of preparing for future sample returns.  Sample return is a very high priority in the Mars and space science communities, and many consider it essential for determining whether there has ever been life on Mars.

So the “wicked” challenges of planetary protection are only going to mount in the years ahead.

 

 

 

 

 

 

 

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NASA Panel Supports Life-Detecting Lander for Europa; Updated

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Artist conception of water vapor plumes coming from beneath the thick ice of Jupiter’s moon Europa. The plumes have not been definitively detected, but Hubble Space Telescope images make public earlier this month appear to show plume activity in an area where it was detected once before.  How will this finding affect decision-making about a potential NASA Europa lander mission? (NASA)

As I prepare for the Astrobiology Science Conference (Abscicon) next week in Arizona, I’m struck by how many speakers will be discussing Europa missions, Europa science, ocean worlds and habitability under ice.  NASA’s Europa Clipper mission to orbit that moon, scheduled for launch to the Jupiter system in the mid 2020s, explains part of the interest, but so too does the unsettled fate of the Europa lander concept.

The NASA Science Definition Team that studied the Europa lander project will both give a science talk at the conference and hold an afternoon-long science community meeting on their conclusions.  The team argued that landing on Europa holds enormous scientific promise, most especially in the search for life beyond Earth.

But since the Europa lander SDT wrote its report and took its conclusions public early this year, the landscape has changed substantially.  First, in March, the Trump Administration 2018 budget eliminated funding for the lander project.  More than half a billion dollars have been spent on Europa lander research and development, but the full project was considered to be too expensive by the White House.

Administration budget proposals and what ultimately become budget reality can be quite different, and as soon as the Europa lander was cancelled supporters in Congress pushed back.  Rep. John Culberson (R-Tex.) and chair of the House subcommittee that oversees the NASA budget, replied to the proposed cancellation by saying “NASA is a strategic national asset and I have no doubt NASA will receive sufficient funding to complete the most important missions identified by the science community, including seeking out life in the oceans of Europa.”

More recently, researchers announced additional detections of plumes of water vapor apparently coming out of Europa — plumes in the same location as a previous apparent detection.  The observing team said they were confident the difficult observation was indeed water vapor, but remained less than 100 percent certain.  (Unlike for the detection of a water plume on Saturn’s moon Enceladeus, which the Cassini spacecraft photographed, measured and flew through.)

So while suffering a serious blow in the budgeting process, the case for a Europa lander has gotten considerably stronger from a science and logistics perspective.  Assuming that the plume detections are accurate, a lander touching down in that general area would potentially have some access to surface H20 that was in the vast global ocean under the ice not too long ago.

Science fiction writer and proto-astrobiologist Arthur C. Clarke famously wrote decades ago that the first life found beyond Earth would most likely be in the oceans of Europa.  In the early 1980s he wrote a sequel to “2001:  A Space Odyssey” called “2010:  Odyssey Two”, with life under the ice of Europa central to the plot.

At the climactic moment in the novel, the hero returns to the iconic computer HAL which sends out this message:

ALL THESE WORLDS ARE YOURS – EXCEPT EUROPA.
ATTEMPT NO LANDINGS THERE.

Hopefully Congress and the White House, if not HAL, can be persuaded otherwise.

Here is a column I wrote about the Europa lander SDT in February:

 

Artist rendering of a potential life-detecting lander mission to Europa that would follow on the Europa Clipper orbiter mission. In the background is Jupiter. NASA/JPL/Caltech

It has been four long decades since NASA has sent an officially-designated life detection mission into space.  The confused results of the Viking missions to Mars in the mid 1970s were so controversial and contradictory that scientists — or the agency at least — concluded that the knowledge needed to convincingly search for extraterrestrial life wasn’t available yet.

But now, a panel of scientists and engineers brought together by NASA has studied a proposal to send a lander to Jupiter’s moon Europa and, among other tasks, return to the effort of life-detection.

In their recommendation, in fact, the NASA-appointed Science Definition Team said that the primary goal of the mission would be “to search for evidence of life on Europa.”

The other goals are to assess the habitability of Europa by directly analyzing material from the surface, and to characterize the surface and subsurface to support future robotic exploration of Europa and its ocean.

Scientists agree that the evidence is quite strong that Europa, which is slightly smaller than Earth’s moon, has a global saltwater ocean beneath its deep ice crust, and that it contains twice as much water as exists on Earth.

For the ocean to be liquid there must be substantial sources of heat — from tidal heating based on the shape of its orbits, or from heat emanating from radioactive decay and entering the ocean through hydrothermal vents.  All could potentially provide an environment where life could emerge and survive.

Kevin Hand of the Jet Propulsion Laboratory is a specialist in icy worlds and is deputy project scientist for the Europa project.  He was one of the co-chairs of the Science Definition Team (SDT) and he said the group was ever mindful of the complicated history of the Viking missions.  He said that some people called Viking a “failure” because it did not clearly identify life, but he described that view as “entirely unscientific.”

“It would be misguided to set out to ‘find life’,” he told me.  “The real objective is to test an hypothesis – one we have that if you bring together the conditions for life as we know them, then they might come together and life can inhabit the environment.

“As far as we can tell, Europa has the water, the elements and the energy needed to create a habitable world.  If the origin of life involves some relatively easy processes, then it just might be there on Europa.”

This artist’s rendering shows NASA’s Europa orbiter mission spacecraft, which is being developed for a launch sometime in the 2020s. The mission would place a spacecraft in orbit around Jupiter in order to perform a detailed investigation of the planet’s moon Europa. The spacecraft will arrive at Jupiter after a multi-year journey, orbiting the gas giant every two weeks for a series of 45 flybys of Europa. NASA generally sends orbiters to a planet or moon before sending a lander. (NASA)

The conclusions of the SDT team, which is made is up of dozens of scientists and engineers, will set the stage for further review, rather than for immediate action.  The report goes to NASA, where it is assessed in relation to other compelling and competing missions.  Both the Congress and White House can and do weigh in

If it is approved, the Europa lander mission would be a companion to the already funded Europa multiple flyby mission scheduled to launch in the 2020s.  While that spacecraft, the Europa Clipper, would have some capacity to determine whether or not the icy moon is habitable, a lander would be needed to search for actual signs of life.

A mission to Europa was a top priority of the 2010 Decadal Review, a synthesis of potential projects in various disciplines that is reviewed by the National Research Council of the National Academy of Sciences.

Kevin Hand of JPL, the deputy science
lead for the Europa project.

Its recommendations from the Decadal Review are generally followed by NASA.  It remains unclear whether the Europa lander is a natural follow-on to the Europa Clipper or a new initiative to be judged on its own.  But the project does have strong support — last year Rep. John Culberson (R-Tex.) pushed a bill through Congress making it illegal to not send a lander to Europa.

Although there are many hurdles to clear for the Europa lander, the SDT report is nonetheless a rather momentous event since it strongly recommends a life-detection mission.  So I thought it was worthwhile to include the entire preface of the team’s conclusions.

“The Europa Lander Science Definition Team Report presents the integrated results of an intensive science and engineering team effort to develop and optimize a mission concept that would follow the Europa Multiple Flyby Mission and conduct the first in situ search for evidence of life on another world since the Viking spacecraft on Mars in the 1970s.

The Europa Lander mission would be a pathfinder for characterizing the biological potential of Europa’s ocean through direct study of any chemical, geological, and possibly biological, signatures as expressed on, and just below, the surface of Europa. The search for signs of life on Europa’s surface requires an analytical payload that performs quantitative organic compositional, microscopic, and spectroscopic analysis on five samples acquired from at least 10 cm beneath the surface, with supporting context imaging observations.

This mission would significantly advance our understanding of Europa as an ocean world, even in the absence of any definitive signs of life, and would provide the foundation for the future robotic exploration of Europa.”

(Here is the full Europa lander SDT report.)

Europa is slightly smaller than the size of our moon, and is broadly agreed to have a large ocean under its 10 to 15 miles ice crust. It orbits Jupiter every 3.5 days. That promixity, coupled with the fact that Europa has a slightly elliptical rather than circular orbit, create the tidal “flexing” and thus heating that can keep water liquid. (NASA)
 

Hand said that a lander would be a natural complement to the Europa Clipper, which is being designed to orbit Jupiter and pass by Europa 45 times at altitudes varying from 1675 miles to 16 miles.  The flybys, he said, could potentially identify cracks and fissures in the crust of the moon, and thereby help identify where a lander should touch down.

What’s more, images taken by the Hubble Space Telescope in 2012 suggest that Europa may be spitting out water in plumes that those clearly detected on Saturn’s moon, Enceladus.

“If a plume was identified during a flyby, you better believe that we would do all we could to land somewhere close to it.  The goal is to get as near as possible to the water coming out from under the crust because that’s how we’ll best learn whether that water has complex organic molecules, nitrogen compounds needed for life and possibly life itself.”

If the lander project does get the green light in the months (or years) ahead, NASA would then put out a call to propose instruments that could search for the various chemical building blocks and manifestations life, as well morphological signs that life once was present.  The search for life, in other words, would involve checking the boxes of building blocks or known molecular signs of possible life as they are found (or not found.)

This is quite a different approach from that used during the Viking missions.

Famously, the so-called “Labelled Release” experiments on both Viking 1 and Viking 2 met the criteria for having detected life as set out by NASA scientists before the mission began.  Those criteria involved the detection of metabolism, the chemical processes that occur within a living organism in order to maintain life.  A detection would imply the presence of life right on the harsh, irradiated Martian surface.

In the LR experiment, a drop of very dilute aqueous nutrient solution was dropped into a sample collected of Martian soil. The nutrients (seven molecules that were products of the Miller-Urey experiment) were tagged with radioactive carbon 14 and the air above the soil was monitored for the evolution of radioactive CO2 gas.  The presence of the gas was interpreted as evidence that microorganisms in the soil had metabolized one or more of the nutrients.

A picture of the Martian surface, as seen by NASA’s Viking 2 lander in 1976.

The LR was followed with a control experiment, and the results consistently met the criteria for having detected “life.”  Two other biology experiments on Viking,  however, came up negative, including the one considered most conclusive — that no carbon-based organic material was detected in the soil, except for one interpreted as contamination from Earth.

Subsequent Mars missions have strongly suggested that those organics interpreted as contamination were, in fact, organics interacting with perchlorate molecules now known to be common on the Martian surface.  But despite this revision, the Mars science community remains broadly skeptical of the Labelled Release results, arguing that the CO2 could have been produced without biology.  That, however, has not stopped LR principal investigator Gilbert Levin, and some others, from arguing now for forty years that the experiment did find life, creating  a controversy that NASA has long struggled with.

Hand said that in hindsight, “we can see that it didn’t make sense to look for metabolism until we knew a lot more.  We need to follow the water, follow the carbon, follow the nitrogen, follow the complex molecules, and if all of that succeeds then we look for a living, breathing creature.”

One of the inspirations for the hypothesis that Europa might harbor life under and within its ice is the recognition that frozen Antarctica also is home to microbial life.  The most significant laboratory is Lake Vostok, an enormous collection of water beneath more than two miles of Antarctic ice.

Researchers have determined that microbial life exists miles down through the ice.  The distribution is small — something like 100 cells per milliliter of melted ice — but researchers have been trying for years to drill down into the lake and determine if the lake itself is home to more abundant life.  The research has been done primarily by Russian scientists and engineers, and has been slowed by the harsh conditions and innumerable technical problems.

Three dimensional model of Lake Vostok drilling. (National Science Foundation)

But as a proof of concept, Hand said, Lake Vostok and other subglacial lakes in Antarctica show that life can survive in freezing conditions.  He said the science teams recommended that any life detection instrument that might go to Europa be able to identify life in the very low concentrations found at Vostok.

Tori Hoehler, a research scientist at NASA’s Ames Research Center, is a specialist in microbial life in low energy environments (like Vostok and perhaps Europa,) and he is also a member of the Europa lander science definition team.

“Our present understanding of Europa suggests that it is habitable, but it is more difficult to constrain how abundant or productive a Europan biosphere — should one exist — might be.  For that reason, a conservative approach is to look to some of Earth’s most sparsely populated ecosystems when setting measurement targets for the lander.”

But however low that abundance might be, the detection of anything with characteristics of life on Europa would be a huge advance for science.

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NASA Panel Supports Life-Detecting Lander for Europa

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Artist rendering of a potential life-detecting lander mission to Europa that would follow on the Europa Clipper orbiter mission that is scheduled to launch in the 2020s.. In the background is Jupiter. (NASA/JPL/Caltech)

It has been four long decades since NASA has sent an officially-designated life detection mission into space.  The confused results of the Viking missions to Mars in the mid 1970s were so controversial and contradictory that scientists — or the agency at least — concluded that the knowledge needed to convincingly search for extraterrestrial life wasn’t available yet.

But now, a panel of scientists and engineers brought together by NASA has studied a proposal to send a lander to Jupiter’s moon Europa and, among other tasks, return to the effort of life-detection.

In their recommendation, in fact, the NASA-appointed Science Definition Team said that the primary goal of the mission would be “to search for evidence of life on Europa.”

The other goals are to assess the habitability of Europa by directly analyzing material from the surface, and to characterize the surface and subsurface to support future robotic exploration of Europa and its ocean.

Scientists agree that the evidence is quite strong that Europa, which is slightly smaller than Earth’s
moon, has a global saltwater ocean beneath its deep ice crust, and that it contains twice as much water as exists on Earth.

For the ocean to be liquid there must be substantial sources of heat — from tidal heating based on the shape of its orbits, or from heat emanating from radioactive decay and entering the ocean through hydrothermal vents.  All could potentially provide an environment where life could emerge and survive.

Kevin Hand of the Jet Propulsion Laboratory is a specialist in icy worlds and is deputy project scientist for the Europa project.  He was one of the co-chairs of the Science Definition Team (SDT) and he said the group was ever mindful of the complicated history of the Viking missions.  He said that some people called Viking a “failure” because it did not clearly identify life, but he described that view as “entirely unscientific.”

“It would be misguided to set out to ‘find life’,” he told me.  “The real objective is to test an hypothesis – one we have that if you bring together the conditions for life as we know them, then they might come together and life can inhabit the environment.

“As far as we can tell, Europa has the water, the elements and the energy needed to create a habitable world.  If the origin of life involves some relatively easy processes, then it just might be there on Europa.”

This artist’s rendering shows NASA’s Europa orbiter mission spacecraft, which is being developed for a launch sometime in the 2020s.  The mission would place a spacecraft in orbit around Jupiter in order to perform a detailed investigation of the planet’s moon Europa. The spacecraft will arrive at Jupiter after a multi-year journey, orbiting the gas giant every two weeks for a series of 45 flybys of Europa.  NASA generally sends orbiter or flyby mission to a destination before attempting a landing. (NASA/JPL-Caltech)

The conclusions of the SDT team, which is made is up of dozens of scientists and engineers, will set the stage for further review, rather than for immediate action.  The report goes to NASA, where it is assessed in relation to other compelling and competing missions.  Both the Congress and White House can and do weigh in.

If it is approved, the Europa lander mission would be a companion to the already funded Europa multiple flyby mission scheduled to launch in the 2020s.  While that spacecraft, the Europa Clipper, would have some capacity to determine whether or not the icy moon is habitable, a lander would be needed to search for actual signs of life.

A mission to Europa was a top priority of the 2010 Decadal Review, a synthesis of potential projects in various disciplines that is reviewed by the National Research Council of the National Academy of Sciences.

Kevin Hand of JPL, the deputy science lead for the Europa project.

Its recommendations from the Decadal Review are generally followed by NASA.  It remains unclear whether the Europa lander is a natural follow-on to the Europa Clipper or a new initiative to be judged on its own.  But the project does have strong support — last year Rep. John Culberson (R-Tex.) pushed a bill through Congress making it illegal to not send a lander to Europa.

Although there are many hurdles to clear for the Europa lander, the SDT report is nonetheless a rather momentous event since it strongly recommends a life-detection mission.  So I thought it was worthwhile to include the entire preface of the teams’s conclusions.

“The Europa Lander Science Definition Team Report presents the integrated results of an intensive science and engineering team effort to develop and optimize a mission concept that would follow the Europa Multiple Flyby Mission and conduct the first in situ search for evidence of life on another world since the Viking spacecraft on Mars in the 1970s.

The Europa Lander mission would be a pathfinder for characterizing the biological potential of Europa’s ocean through direct study of any chemical, geological, and possibly biological, signatures as expressed on, and just below, the surface of Europa. The search for signs of life on Europa’s surface requires an analytical payload that performs quantitative organic compositional, microscopic, and spectroscopic analysis on five samples acquired from at least 10 cm beneath the surface, with supporting context imaging observations.

This mission would significantly advance our understanding of Europa as an ocean world, even in the absence of any definitive signs of life, and would provide the foundation for the future robotic exploration of Europa.”

(Here is the full Europa lander SDT report.)

Europa is slightly smaller than the size of our moon, and is broadly agreed to have a large ocean under its 10 to 15 miles ice crust. It orbits Jupiter every 3.5 days.  That promixity, coupled with the fact that Europa has a slightly elliptical rather than circular orbit, create the tidal “flexing” and thus heating that can keep water liquid.  (NASA)

Hand said that a lander would be a natural complement to the Europa Clipper, which is being designed to orbit Jupiter and pass by Europa 45 times at altitudes varying from 1675 miles to 16 miles.  The flybys, he said, could potentially identify cracks and fissures in the crust of the moon, and thereby help identify where a lander should touch down.

What’s more, images taken by the Hubble Space Telescope in 2012 suggest that Europa may be spitting out water in plumes that those clearly detected on Saturn’s moon, Enceladus.

“If a plume was identified during a flyby, you better believe that we would do all we could to land somewhere close to it.  The goal is to get as near as possible to the water coming out from under the crust because that’s how we’ll best learn whether that water has complex organic molecules, nitrogen compounds needed for life and possibly life itself.”

If the lander project does get the green light in the months (or years) ahead, NASA would then put out a call to propose instruments that could search for the various chemical building blocks and manifestations life, as well morphological signs that life once was present.  The search for life, in other words, would involve checking the boxes of building blocks or known molecular signs of possible life as they are found (or not found.)

This is quite a different approach from that used during the Viking missions.

Famously, the so-called “Labelled Release” experiments on both Viking 1 and Viking 2 met the criteria for having detected life as set out by NASA scientists before the mission began.  Those criteria involved the detection of metabolism, the chemical processes that occur within a living organism in order to maintain life.  A detection would imply the presence of life right on the harsh, irradiated Martian surface.

In the LR experiment, a drop of very dilute aqueous nutrient solution was dropped into a sample collected of Martian soil.The nutrients (seven molecules that were products of the Miller-Urey experiment) were tagged with radioactive carbon 14 and the air above the soil was monitored for the evolution of radioactive 14CO2 gas.  The presence of the gas was interpreted as evidence that microorganisms in the soil had metabolized one or more of the nutrients.

A picture of the Martian surface, as seen by NASA’s Viking 2 lander in 1976. (NASA)

The LR was followed with a control experiment, and the results consistently met the criteria for having detected “life.”  Two other biology experiments on Viking,  however, came up negative, including the one considered most conclusive — that no carbon-based organic material was detected in the soil, except for one interpreted as contamination from Earth.

Subsequent Mars missions have strongly suggested that those organics interpreted as contamination were, in fact, organics interacting with perchlorate molecules now known to be common on the Martian surface.  But despite this revision, the Mars science community remains broadly skeptical of the Labelled Release results, arguing that the CO2 could have been produced without biology.  That, however, has not stopped LR principal investigator Gilbert Levin, and some others, from arguing now for forty years that the experiment did find life, creating  a controversy that NASA has long struggled with.

Hand said that in hindsight, “we can see that it didn’t make sense to look for metabolism until we knew a lot more.  We need to follow the water, follow the carbon, follow the nitrogen, follow the complex molecules, and if all of that succeeds then we look for a living, breathing creature.”

One of the inspirations for the hypothesis that Europa might harbor life under and within its ice is the recognition that frozen Antarctica also is home to microbial life.  The most significant laboratory is Lake Vostok, an enormous collection of water beneath more than two miles of Antarctic ice.

Researchers have determined that microbial life exists miles down through the ice.  The distribution is small — something like 100 cells per milliliter of melted ice — but researchers have been trying for years to drill down into the lake and determine if the lake itself is home to more abundant life.  The research has been done primarily by Russian scientists and engineers, and has been slowed by the harsh conditions and innumerable technical problems.

Three dimensional model of Lake Vostok drilling. (Credit: National Science Foundation)

But as a proof of concept, Hand said, Lake Vostok and other subglacial lakes in Antarctica show that life can survive in freezing conditions.  He said the science teams recommended that any life detection instrument that might go to Europa be able to identify life in the very low concentrations found at Vostok.

Tori Hoehler, a research scientist at NASA’s Ames Research Center, is a specialist in microbial life in low energy environments (like Vostok and perhaps Europa,) and he is also a member of the Europa lander science definition team.

“Our present understanding of Europa suggests that it is habitable, but it is more difficult to constrain how abundant or productive a Europan biosphere — should one exist — might be.  For that reason, a conservative approach is to look to some of Earth’s most sparsely populated ecosystems when setting measurement targets for the lander.”

But however low that abundance might be, the detection of anything with characteristics of life on Europa would be a huge advance for science.

NASA has announced two upcoming town hall meetings to discuss the Science Definition Team report and receive feedback from the science community. The first will be on March 19, in conjunction with the 2017 Lunar and Planetary Science Conference (LPSC) at The Woodlands, Texas. The second event will be on April 23 at the Astrobiology Science Conference (AbSciCon) in Mesa, Arizona.

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More Evidence of Water Plumes On Europa Increases Confidence That They’re For Real

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 Figure 2: This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The Hubble data were taken on January 26, 2014. The image of Europa, superimposed on the Hubble data, is assembled from data from the Galileo and Voyager missions. Credits: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center Image comparison of 2014 transit and 2012 Europa aurora observations

This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The Hubble data were taken on January 2014, and appear to show plumes that spit out as much as 125 miles.  The image of Europa, superimposed on the Hubble data, is assembled from data from the Galileo and Voyager missions. (NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center)

Europa is a moon no bigger than our own and is covered by deep layers of ice, but it brings with it a world of promise.  Science fiction master and sometimes space visionary Arthur C. Clarke, after all,  named it as the most likely spot in our solar system to harbor life, and wrote a “2001: A Space Odyssey”  follow-up based in part on that premise.

Many in the planetary science and astrobiology communities are similarly inclined and have supported a specifically Europa mission geared to learning more about what is generally considered to be a large ocean beneath that ice.

Along the way, Europa became the only object deemed by Congress to be an obligatory NASA destination, and formal plans for such a voyage have been under way — however slowly — for several years.  Formal development of the “Europa Clipper” flyby project began last year, after a half decade of conceptual work.

The logic for the flyby got a major boost on Monday when a team using the Hubble Space Telescope reported that they had most likely detected plumes of water erupting out of Europa on three separate occasions.

Because of the difficulty of the observation — and the fact that plumes were found on 3 out of 10 passes — nobody was willing to claim that the finding was definitive.  But coupled with an earlier identification of a Europa plume by a different team using a different technique, the probability that the plumes are real is getting pretty high.

And if there really are plumes of water vapor or ice crystals being pushed through Europa’s thick surface of ice, then the implications for the search for signs of habitability and of life on Europa are enormous.

“Europa is surely one of the most compelling astrobiological targets in solar system with its apparent saline oceans,” said William Sparks, an astronomer with Space Telescope Science Institute in Baltimore and lead author of the Europa paper, to be published in The Astrophysical Journal.

“And now there’s the real possibility that we can explore for organics or even signs of life without drilling into the ice.”  In other words, the plumes could allow NASA to collect material once in the oceans of Europa via a flyby, rather than requiring a landing and a subsequent piercing through miles of ice.

Bizarre features on Europa’s icy surface suggest a warm interior. This view of the surface and shows a color image set within a larger mosaic of low-resolution monochrome images. The Galileo spacecraft was able to survey only a small fraction of Europa's surface in color at high resolution; a future mission would include a high-resolution imaging capability to capture a much larger part of the moon's surface. (NASA/JPL-Caltech)
Beautiful and mysterious features on Europa’s icy surface suggest a warm interior and hint at the geology that could allow water to break through a weak point and erupt as a plume. This view of the surface and shows a color image set within a larger mosaic of low-resolution monochrome images. The Galileo spacecraft was able to survey only a small fraction of Europa’s surface in color at high resolution; a future mission would include a high-resolution imaging capability to capture a much larger part of the moon’s surface. (NASA/JPL-Caltech)

The findings make it increasingly likely that there are at least two moons in our solar system that have spurting plumes of water vapor.  Saturn’s moon Enceladus definitely has plumes — the Cassini spacecraft traveled through one of them, collecting data — and now there’s good reason to conclude Europa does as well.  This raises the possibility that icy water worlds around the galaxy are spouting out their insides, and some day they might be measurable as well.

Sparks and other scientists on a NASA teleconference repeatedly emphasized, however, that more needed to be done before the presence of Europa plumes could be deemed conclusive.

“These are challenging observations pushing the limits of Hubble,” he said of their work, which used the Space Telescope Imaging Spectrograph to capture far ultraviolet radiation.

To get their results they used the “transit” method of observing Europa, a technique pioneered by exoplanet astronomers working to understand the compositions of the atmospheres of planets far, far away.  That scientists studying possible Europan plumes and methane compositions around distant planets demonstrates just how much cross pollination exists between astronomy, planetary science, astrobiology and exoplanet research have become.

“The atmosphere of an extrasolar planet blocks some of the starlight that is behind it,” Sparks explained. “If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter.”

The results were collected over a 15 month period, largely in 2014.  It took several years to process the information and check and recheck the instruments and methodologies to limit the possibility of a false positive.

The findings support earlier evidence for water plumes on Europa detected by a team led by Lorenz Roth of Southwest Research Institute in San Antonio.  They concluded that water vapor had erupted from south polar region of Europa and reached more than 100 miles into space.

Although both teams used Hubble’s Space Telescope Imaging Spectrograph (STIS) instrument, each used an independent method to arrive at the same conclusion.

 

Europa orbits Jupiter every 3 and a half days, and on every orbit it passes in front of the planet. That choreography raises the possibility of plumes being seen as silhouettes absorbing the background light of Jupiter. (A. Field; STScI)
Europa orbits Jupiter every 3 and a half days, and on every orbit it passes in front of the planet. That choreography raises the possibility of plumes being seen as silhouettes absorbing the background light of Jupiter. (A. Field; STScI)

Europa is cold — very cold.  The surface temperature at the equator never rises above minus 260 degrees Fahrenheit. At the poles of the moon, the temperature never rises above minus 370 F.

So how can there be a large ocean beneath the ice to begin with?

The answer involves heat produced by “flexing” of Europa based on its eccentric orbit and the gravitational pull of Jupiter.

This is how a NASA article described it:

“As Europa’s distance from Jupiter changes over the course of its orbit, Jupiter’s gravitational attraction changes, since gravitational force is dependent on distance.  As a result, the tidal bulge raised by Jupiter goes up and down. This flexing causes heating of Europa’s subsurface.”

But Europa, like Earth and every other celestial body, has also been on the receiving end over the eons of material from asteroids, comets, smaller planets and even deep space.  In addition to basic elements and compounds, Europa likely had organic material — the building blocks of life — delivered to it as well.

What’s more, the moon no doubt contains long-lived radioactive isotopes brought to it after formation. The decay of these isotopes would produce radiogenic heating, and may play a role in keeping the Europan ocean wet.

Results from prior missions strongly suggest that this water on Europa is salty, adding to the prospects for life.  And in 2016, a study suggested that Europa produces 10 times more oxygen than hydrogen, which is similar to the ratio on Earth.

 

cryovolcanoesn in europa
Scenario for getting water to Europa’s surface. Artist’s conception of ridges and fractures of Europa.  The ice cover is estimated to be between 6 and 13 miles thick. (NASA/JPL-Caltech)

So, that there may well be a habitable ocean between the ice mantle and rocky insides of Europa is well accepted.  How might some of that water rise up to the surface and ultimately erupt as a plume?

Britney Schmidt, assistant professor at the School of Earth and Atmospheric Sciences at Georgia Institute of Technology in Atlanta, said it has long been hypothesized that vents open at times between the surface and the water below — if not the oceans, then perhaps some lakes closer to the surface.

This is hypothesized to be most likely in chaos terrain, where features such as ridges, cracks, and plains (be they of ice or rock) appear jumbled and enmeshed with one another.  Europa is covered with this kind of geology.

Schmidt, who has studied Europa extensively, described the upwellings as “cryovolcanoes” — small fingers of liquid water pushed up to the surface by the intense pressure of miles of ice above these oceans.

While the presumptive plume activity appears to be most common near the south pole, it is also found elsewhere, including one detection near the equator.

 

NASA hopes the Europan Clipper will fly in the early or mid 2020s and will search for signs of habitability. It is expected to circle the moon for three years. (NASA/JPL-Caltech)
NASA hopes the Europan Clipper will fly in the early or mid 2020s and will search for signs of habitability. It is expected to circle the moon for three years. (NASA/JPL-Caltech)

Europa has been on NASA’s radar screen for some time.  The National Research Council’s once-a-decade review for planetary science, issued in 2013, made exploration of Europa the agency’s highest-priority mission in that arena. The agency generally follows the NRC recommendations.

As currently conceived, the mission would send a probe and lander to the moon, to be launched in the 2020s. Funding for the estimated $2.3 billion project remains a major issue, but last year NASA asked scientists and engineers to propose designs for instruments. Thirty-three proposals came in and nine were selected.

As it is being developed, the mission would send a solar-powered spacecraft into a long, looping orbit around Jupiter to then perform three-years of repeated close flybys of Europa. In total, the mission would perform 45 flybys at altitudes ranging from 16 miles to 1,700 miles (25 kilometers to 2,700 kilometers).

But later action in Congress — where Rep. John Culberson, a Texas Republican who represents the area including NASA headquarters,  has pushed hard for a major Europa mission — added a lander to the project, to be launched two years after the Clipper.   Culberson, chair of the House subcommittee that funds NASA, strongly believes that NASA will find the first evidence for life beyond Earth in the ocean beneath the thick surface ice.

 Rep. John Culberson, R-Texas, is chairman of the House Subcommittee on Commerce, Justice, Science, which oversees NASA funding. Culberson is a strong proponent of missions to Europa in search of extraterrestrial life. (Photo By Tom Williams/CQ Roll Call)
Rep. John Culberson, R-Texas, chairman of the House Subcommittee on Commerce, Justice, Science, is an active proponent of missions to Europa to search of extraterrestrial life. His subcommittee oversees NASA funding. (Photo By Tom Williams/CQ Roll Call)

The selected science instruments includes cameras and spectrometers to produce high-resolution images of Europa’s surface and determine its composition. An ice penetrating radar will determine the thickness of the moon’s icy shell and search for subsurface lakes similar to those beneath Antarctica. The mission also will carry a magnetometer to measure strength and direction of the moon’s magnetic field, which will allow scientists to determine the depth and salinity of its ocean.

A thermal instrument will scour Europa’s frozen surface in search of recent eruptions of warmer water, while additional instruments will search for evidence of water and tiny particles in the moon’s thin atmosphere.

Curt Niebur, project scientist for the Europa mission, was on the teleconference call as well, and described the increasing possibility that the Clipper will find Europan plumes as enormously exciting and important.  He said that the spacecraft will have the ability to change course and head to an area experiencing a plume — should one erupt.

He also said the vehicle could potentially pass through a plume like Cassini did with one of the plumes of Enceladus.  Those plumes are larger than anything tentatively detected on Europa and are more predictable in their timing and locations.

But who knows what might be possible?

“We found out a lot about Enceladus by flying through the plume and sampling plume material,” Niebur said.  “We would kill to have that kind of information for Europa.”

 

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