American attention regarding space missions is, not surprisingly, focused primarily on NASA missions. But there is a lot more exploration underway, and we should know about it. This is a guest column by Elizabeth Tasker, an Associate Professor at the Japan Aerospace Exploration Agency, JAXA, and whose book, “The Planet Factory”, comes out in November in the USA. Here she explains the upcoming Japanese mission to the moons of Mars that will include sample return.
— Marc Kaufman
By Elizabeth Tasker
The global success rate for sending missions to land on the moons of Mars has hardly been impressive — coming in at zero out of three attempts. They were all led by the Russian (or former Soviet) space agencies, in collaboration with organizations ranging from the Chinese and Bulgarian space agencies to the Paris Observatory and the U.S. Planetary Society.
Now the Japanese space agency JAXA has approved its own mission to Phobos and Deimos, scheduled to launch from the Tanegashima Space Center in September 2024.
The Martian Moons eXploration (MMX) spacecraft will arrive at Mars in August 2025 and spend the next three years exploring the two moons and the environment around Mars. During this time, the spacecraft will drop to the surface of one of the moons and collect a sample to bring back to Earth. Probe and sample are scheduled to return to Earth in the summer of 2029.
Mars takes its name from the god of war in ancient Greek and Roman mythology. The Greek god Ares became Mars in the Roman adaptation of the deities. Mars’s two moons are named for Phobos and Deimos; in legend the twin sons of Ares who personified fear and panic.
Today, what the moons together personify is a compelling mystery, one regarding how in reality they came to be.
Both Martian moons are small, with Phobos’s average diameter measuring 22.2km, while the even smaller Deimos has an average size of just 13km. This makes even Phobos’s surface area only comparable to that of Tokyo. Their diminutive proportions means that the moons resemble asteroids, with irregular structures due to their gravity being too weak to pull them into spheres.
This leads to the question that has inspired a long-running debate: Were Phobos and Deimos formed during an impact with Mars, or are they asteroids that have been captured by Mars’s gravity?
Our own Moon is thought to have been created when a Mars-sized body slammed into the early Earth. Debris from the collision was thrown into the Earth’s orbit where is coalesced into our only natural satellite.
A similar scenario is possible for Phobos and Deimos. In the late stages of our solar system’s formation, giant impacts such as the one that struck the Earth were relatively common.
Mars shows possible evidence for one such collision with a body the size of our moon. The Martian surface has a dichotomy consistent with such an event, with the northern hemisphere sitting an average of 5.5km lower than the southern side. During such impacts, debris could have been thrown up from the Martian surface to birth the two moons.
An alternative scenario is that the resemblance of Phobos and Deimos to asteroids is not coincidental.
The two moons may have originally been part of the asteroid belt; a band of rocky left-overs from the planet formation process that circle the Sun between Mars and Jupiter. Scattered inwards towards the Sun during a chance collision, the asteroids may have been snagged into orbit by Mars’s gravity.
Observations of both moons suggest that their surface material is similar to that of other asteroids.
Disentangling these two possible births is the primary goal for the Martian Moons eXploration mission. If the moons were formed from the body of Mars itself, their rock type should resemble that of Mars. On the other hand, if the pair were captured then they would have formed in a different part of the Solar System with their own distinct composition.
Both options would reveal a great deal about the formation of our Solar System.
The young Mars is suspected to have been similar to the early Earth. If Phobos and Deimos formed during this time, the moons could be preserved time capsules of what conditions were like on the planets in this epoch. This would help us understand the formation of the Earth and maybe even the development of habitability on ancient Mars and Earth.
On the other hand, the Earth’s water is suspected to have been delivered to our planet after its formation by impacts from icy meteorites. This water delivery service may have originated in the asteroid belt (one rocky member of which is currently the destination of JAXA’s Hayabusa2).
If Phobos and Deimos are captured asteroids, they may be kin to the ice-packed rocks that hit the early Earth, revealing information about how volatiles were circulated about our Solar System.
The Martian Moons eXploration spacecraft is planning to study both moons and collect rock samples from Phobos. Phobos’s orbit takes it closer to Mars than Deimos, circling the planet at about 6,000 km above the surface. For comparison, the Moon is 385,000 km above the Earth.
This close proximity means that the surface of Phobos should have a loose layer of regolith or soil sprayed up from Mars during more recent impacts with meteorites. Samples taken from Phobos are therefore expected to contain Martian meteorites and the moon’s own material from deeper down.
This extra Martian regolith may be very different from the rocks that make it to Earth, such as the famous ALH84001 which was initially thought to contain a range of signs that life once existed in the rock. (The scientific consensus now is that the biosignatures can be explained as coming from processes other than life.)
The shorter journey to the close-by moon allows the transfer of lower density material that would never survive the trip to Earth. The regolith will also originate from all over the planet, rather than the small region of Mars that has been explored by landed rovers, providing a more wide spread sample than has previously been analyzed.
Excitement for the science a Mars moon mission could bring has led to strong international involvement. On April 10th this year, the president of the French space agency, CNES, visited the president of JAXA in Tokyo for a signing ceremony that formalized the agreement between the two agencies. CNES will be developing one of the key instruments for the mission as well as adding their expertise on flight dynamics for the tricky maneuvers around the Martian moons.
The planned French instrument is a Near-Infrared Spectrometer (NIRS), which combines a high-resolution infrared camera with the ability to analyze each pixel to determine the composition of the rock. Similar instruments have previously flown on ESA’s Mars Express and ExoMars, but with an image pixel size an order of magnitude larger than that now planned for the Martian Moons eXploration mission. The French space agency will also explore the possibility of providing a rover to explore the surface of Phobos on microscopic scales.
There are also plans for an instrument to be developed by NASA, which has put out an official “Announcement of Opportunity” inviting proposals for the instrument design. This would be a neutron and Gamma ray spectrometer, which probes the abundance of individual elements in the moons, rather than their combination within minerals that NIRS can see.
This will be JAXA’s third mission to sample material from a small body. Hayabusa visited the asteroid Itokawa, bringing back surface material to Earth from the asteroid in seven years ago this month. Its successor, Hayabusa2, is currently traveling to asteroid Ryugu and is expected to arrive in 2018.
With only 1/1000th of the gravity on Earth, landing on Phobos is a challenging task. But if samples can be collected for return to Earth, that will be a major scientific and engineering accomplishment.
Updates for the MMX mission can be found on the mission webpage in English and Japanese. Will you rooting for #TeamImpact or #TeamCapture?
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.
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.”
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.
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, 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.
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.
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.
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.
The Many Worlds site has been down for almost two weeks following the crash of the server used to publish it. We never expected it would take quite this long to return to service, but now we are back with a column today and another one for early next week.
Earth is most fortunate to have vast webs of magnetic fields surrounding it. Without them, much of our atmosphere would have been gradually torn away by powerful solar winds long ago, making it unlikely that anything like us would be here.
Scientists know that Mars once supported prominent magnetic fields as well, most likely in the early period of its history when the planet was consequently warmer and much wetter. Very little of them is left, and the planet is frigid and desiccated.
These understandings lead to an interesting question: if Mars had a functioning magnetosphere to protect it from those solar winds, could it once again develop a thicker atmosphere, warmer climate and liquid surface water?
James Green, director of NASA’s Planetary Science Division, thinks it could. And perhaps with our help, such changes could occur within a human, rather than an astronomical, time frame.
In a talk at the NASA Planetary Science Vision 2050 Workshop at the agency’s headquarters, Green presented simulations, models, and early thinking about how a Martian magnetic field might be re-constituted and the how the climate on Mars could then become more friendly for human exploration and perhaps communities.
It consisted of creating a “magnetic shield” to protect the planet from those high-energy solar particles. The shield structure would consist of a large dipole—a closed electric circuit powerful enough to generate an artificial magnetic field.
Simulations showed that a shield of this sort would leave Mars in the relatively protected magnetotail of the magnetic field created by the object. A potential result: an end to largescale stripping of the Martian atmosphere by the solar wind, and a significant change in climate.
“The solar sytstem is ours, let’s take it,” Green told the workshop. “And that, of course, includes Mars. But for humans to be able to explore Mars, together with us doing science, we need a better environment.”
Is this “terraforming,” the process by which humans make Mars more suitable for human habitation? That’s an intriguing but controversial idea that has been around for decades, and Green was wary of embracing it fully.
“My understanding of terraforming is the deliberate addition, by humans, of directly adding gases to the atmosphere on a planetary scale,” he wrote in an email.
“I may be splitting hairs here, but nothing is introduced to the atmosphere in my simulations that Mars doesn’t create itself. In effect, this concept simply accelerates a natural process that would most likely occur over a much longer period of time.”
What he is referring to here is that many experts believe Mars will be a lot warmer in the future, and will have a much thicker atmosphere, whatever humans do. On its own, however, the process will take a very long time.
To explain further, first a little Mars history.
Long ago, more than 3.5 billion years in the past, Mars had a much thicker atmosphere that kept the surface temperatures moderate enough to allow for substantial amounts of surface water to flow, pool and perhaps even form an ocean. (And who knows, maybe even for life to begin.)
But since the magnetic field of Mars fell apart after its iron inner core was somehow undone, about 90 percent of the Martian atmosphere was stripped away by charged particles in that solar wind, which can reach speeds of 250 to 750 kilometers per second.
Mars, of course, is frigid and dry now, but Green said the dynamics of the solar system point to a time when the planet will warm up again.
He said that scientists expect the gradually increasing heat of the sun will warm the planet sufficiently to release the covering of frozen carbon dioxide at the north pole, will start water ice to flow, and will in time create something of a greenhouse atmosphere. But the process is expected to take some 700 millon years.
“The key to my idea is that we now know that Mars lost its magnetic field long ago, the solar wind has been stripping off the atmosphere (in particular the oxygen) ever since, and the solar wind is in some kind of equilibrium with the outgassing at Mars,” Green said. (Outgassing is the release of gaseous compounds from beneath the planet’s surface.)
“If we significantly reduce the stripping, a new, higher pressure atmosphere will evolve over time. The increase in pressure causes an increase in temperature. We have not calculated exactly what the new equilibrium will be and how long it will take.”
The reason why is that Green and his colleagues found that they needed to add some additional physics to the atmospheric model, dynamics that will become more important and clear over time. But he is confident those physics will be developed.
He also said that the European Space Agency’s Trace Gas Orbiter now circling Mars should be able to identify molecules and compounds that could play a significant role in a changing Mars atmosphere.
So based on those new magnetic field models and projections about the future climate of Mars, when might it be sufficiently changed to become significantly more human friendly?
Well, a relatively small change in atmospheric pressure can stop an astronaut’s blood from boiling, and so protective suits and clothes would be simpler to design. But the average daily range in temperature on Mars now is 170 degrees F, and it will take some substantial atmospheric modification to make that more congenial.
Green’s workshop focused on what might be possible in the mid 21st century, so he hopes for some progress in this arena by then.
One of many intriguing aspects of the paper is its part in an NASA effort to link fundamental models together for everything from predicting global climate to space weather on Mars.
The modeling of a potential artificial magnetosphere for Mars relied, for instance, on work done by NASA heliophysics – the quite advanced study of our own sun.
Chuanfei Dong, an expert on space weather at Mars, is a co-author on the paper and did much of the modeling work. He is now a postdoc at Princeton University, where he is supported by NASA.
He used the Block-Adaptive-Tree Solar-Wind Roe-Type Upwind Scheme (BATS-R-US) model to test the potential shielding effect of an artificial magnetosphere, and found that it was substantial when the magnetic field created was sufficiently strong. Substantial enough, in fact, to greatly limit the loss of Martian atmosphere due to the solar wind.
As he explained, the artificial dipole magnetic field has to rotate to prevent the dayside reconnection, which in turn prevents the nightside reconnection as well.
If the artificial magnetic field does not block the solar winds properly, Mars could lose more of its atmosphere. That why the planet needs to be safely within the magnetotail of the artificial magnetosphere.
In their paper, the authors acknowledge that the plan for an artificial Martian magnetosphere may sound “fanciful,” but they say that emerging research is starting to show that a miniature magnetsphere can be used to protect humans and spacecraft.
In the future, they say, it is quite possible that an inflatable structure can generate a magnetic dipole field at a level of perhaps 1 or 2 Tesla (a unit that measures the strength of a magnetic field) as an active shield against the solar wind. In the simulation, the magnetic field is about 1.6 times strong than that of Earth.
As a summary of what Green and others are thinking, here is the “results” section of the short paper:
“It has been determined that an average change in the temperature of Mars of about 4 degrees C will provide enough temperature to melt the CO2 veneer over the northern polar cap.
“The resulting enhancement in the atmosphere of this CO2, a greenhouse gas, will begin the process of melting the water that is trapped in the northern polar cap of Mars. It has been estimated that nearly 1/7th of the ancient ocean of Mars is trapped in the frozen polar cap. Mars may once again become a more Earth-like habitable environment.
The results of these simulations will be reviewed (with) a projection of how long it may take for Mars to become an exciting new planet to study and to live on.”
Sometimes images arrive that make it clear that the space age is not a throw-away line, but a reality.
This one was taken by a satellite orbiting Mars, and it shows the Earth and the moon. Kind of remarkable, given that the camera — the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter — was 127 million miles away
And HiRISE is not a far-seeing telescope, but rather a camera designed to look down on Mars from 160 to 200 miles away. It’s job (among other tasks) is to image the terrain, measure the compounds and minerals below, and keep an eye on Mars dust storms, climate, and the downhill steaks that periodically appear on some inclines and may contain surface salty water.
The image is a composite image of Earth and its moon, combining the best Earth image with the best moon image from four sets of images acquired on Nov. 20, 2016 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter.
Each was separately processed prior to combining them so that the moon is bright enough to see. The moon is much darker than Earth and would barely be visible at the same brightness scale as Earth. The combined view retains the correct sizes and positions of the two relative to each other.
This is how JPL described the details:
HiRISE takes images in three wavelength bands: infrared, red, and blue-green. These are displayed here as red, green, and blue, respectively. This is similar to Landsat images in which vegetation appears red. The reddish feature in the middle of the Earth image is Australia. Southeast Asia appears as the reddish area (due to vegetation) near the top; Antarctica is the bright blob at bottom-left. Other bright areas are clouds.
What I find especially intriguing about the image is that it is precisely the kind of “direct imaging” that the exoplanet community hopes to some day do with distant planets. With this kind of imaging, scientists not only can detect the glints of water, the presence of land, the dynamics of clouds and climate, but they can also get better spectrographic measurements of what chemicals are present.
Some exoplanets are being painstakingly direct imaged, but the difficulty factor is high and the result is most likely one or two pixels. And since the planets are orbiting stars that send out light that hides any exoplanets present, coronagraphs are needed inside the telescopes to block out the sun and its rays.
Enormous, unfolding “starshades” sent to space may some day perform the same function in tandem with a space telescope. Advocates for the technology say it will provide greater opportunity and sensitivity.
More on this in the weeks ahead.
Here is another Earth/moon image taken by HiRISE in 2007, when our distance Mars was 88 million miles. Here the Earth diameter is about 90 pixels and the moon diameter is 24 pixels.
For years, noted chemist and synthetic life researcher Steven Benner has talked about the necessary role of the element boron in the origin of life.
Without boron, he has found, many of the building blocks needed to form the earliest self-replicating ribonucleic acid (RNA) fall apart when they come into contact with water, which is nonetheless needed for the chemistry to succeed. Only in the presence of boron, Benner found and has long argued, can the formation of RNA and later DNA proceed.
Now, to the delight of Benner and many other scientists, the Curiosity team has found boron on Mars. In fact, as Curiosity climbs the mountain at the center of Gale Crater, the presence of boron has become increasingly pronounced.
And to make the discovery all the more meaningful to Benner, the boron is being found in rock veins. So it clearly was carried by water into the fractures, and was deposited there some 3.5 billion years ago.
Combined with earlier detections of phosphates, magnesium, peridots, carbon and other essential elements in Gale Crater, Benner told me, “we have found on Mars an environment entirely consistent with a what we consider conducive for the origin of life.
“Is it likely that life arose? I’d say yes…perhaps even, hell yes. But it’s also true that an environment conducive to the formation of life isn’t necessarily one conducive to the long-term survival of life.”
Another factor in the Mars-as-habitable story from Benner’s view is that there has never been the kind of water world there that many believe existed on early Earth.
While satellites orbiting Mars and now Curiosity have made it abundantly clear that early Mars also had substantial water in the form of lakes, rivers, streams and perhaps an localized ocean, it was clearly never covered in water.
And that’s good for the origin of life, Benner said.
“We think that a largely arid environment, with water present but not everywhere, is the best one for life to begin. Mars had that but Earth, well, maybe not so much. The problem is how to concentrate the makings of RNA, of life, in a vast ocean. It’s like making a cake in water — all the ingredients will float away.
“But the mineral ensemble they’ve discovered and given us is everything we could have asked for, and it was on a largely dry Mars,” he said. “So they’ve kicked the ball back to us. Now we have to go back to our labs to enrich the chemistry around this ensemble of minerals.”
In his labs, Benner has already put together a process — he calls it his discontinuous synthesis model — whereby all the many steps needed to create RNA and therefore life have been demonstrated to be entirely possible.
What’s missing is a continuous model that would show that process at work, starting with a particular atmosphere and particular minerals and ending up with RNA. That’s something that requires a lot more space and time than any lab experiments would provide.
“This is potentially what Mars provides,” he said,
Benner, it should be said, is not a member of the Curiosity team and doesn’t speak for them.
But his championing of boron as a potentially key element for the origin of life was noted as a guide by one of the Curiosity researchers during a press conference with team members at the American Geophysical Union Dec. 13 in San Francisco. It was at that gathering that the detection of the first boron on Mars was announced.
Benner said he has been in close touch with the two Curiosity instrument teams involved in the boron research and was most pleased that his own boron work — and that of at least one other researcher — had helped inspire the search for and detection of the element on Mars. That other researcher, evolutionary biologist James Stephenson, had detected boron in a meteorite from Mars.
Patrick Gasda, a postdoctoral researcher at Los Alamos National Laboratory, is a member of the Chemistry and Camera (ChemCam) instrument team which identified the boron at Gale Crater. The instrument uses laser technology to identify chemical elements in Martian rocks.
Gasda said at AGU that if the boron they found in calcium sulfate rock veins on Mars behaves there as it does on Earth, then the environment was conducive to life. The ancient groundwater that formed these veins would have had temperatures in the 0-60 degrees Celsius (32-140 degrees Fahrenheit) range, he said, with a neutral-to-alkaline pH.
While the presence of boron (most likely the mineral form borate, Benner said) has increased as the rover has climbed Mount Sharp, the element still makes up only one-tenth of one percent of the rock composition. But to stabilize that process of making RNA, that’s enough.
Benner’s view of Gale Crater and Mars as entirely habitable is not new — the Curiosity team has been saying roughly the same for several years now. But with four full years on Mars the rover keeps adding to the habitability story, and that was the central message from Curiosity scientists speaking at the AGU press conference.
As the rover examines higher, younger layers, the researchers said they were especially impressed by the complexity of the ancient lake environments at Gale when sediments were being deposited, and also the complexity of the groundwater interactions after the sediments were buried.
“There is so much variability in the composition at different elevations, we’ve hit a jackpot,” said John Grotzinger of Caltech, and formerly the mission scientist for Curiosity.
“A sedimentary basin such as this is a chemical reactor. Elements get rearranged. New minerals form and old ones dissolve. Electrons get redistributed. On Earth, these reactions support life.”
This kind of reactivity occurs on a gradient based on the strength of a chemical at donating or receiving electrons. Transfer of electrons due to this gradient can provide energy for life.
While habitability is key to Curiosity’s mission on Mars, much additional science is being done that has different goals or looks more indirectly at the planet’s ancient (or possibly current) ability to support life. Understanding the ancient environmental history of Gale Crater and Mars is a good example.
For instance, the Curiosity team is now undertaking a drilling campaign in progressively younger rock layers, digging into four sites each spaced about 80 feet (about 25 meters) further uphill. Changes in which minerals are present and in what percentages they exist give insights into some of that ancient history.
One clue to changing ancient conditions is the presence of the mineral hematite, a form of the omnipresent iron oxide on Mars. Hematite has replaced magnetite as the dominant iron oxide in rocks Curiosity has drilled recently, compared with the site where Curiosity first found lake bed sediments.
Thomas Bristow of NASA Ames Research Center, who works with the Chemistry and Mineralogy (CheMin) laboratory instrument inside the rover, said Mars is sending a signal. Both forms of iron oxide (hematite and magnetite) were deposited in mudstone in what was once the bottom of a lake, but the increased abundance of hematite higher up Mount Sharp suggests conditions were warmer when it was laid down. There also was probably more interaction between the atmosphere and the sediments.
On a more technical level, an increase in hematite relative to magnetite also indicates an environmental change towards a stronger tug on the iron oxide electrons, causing a greater degree of oxidation (the loss of electrons) in the iron. That would likely be caused by changing atmospheric conditions.
It’s all part of putting together the jigsaw puzzle of Mars circa 3.5 billion years ago.
Returning to the boron story, Benner said that the discovered presence of all the chemicals his group believes are necessary to ever-so-slowly move from prebiotic chemistry to biology provides an enormous opportunity. Because of plate tectonics on Earth and the omnipresence of biology, the conditions and environments present on early Earth when life first arose were long ago destroyed.
But on Mars, the apparent absence of those most powerful agents of change means it’s possible to detect, observe and study conditions in a changed but intact world that just might have given rise to life on Mars. Taken a step further, Mars today could provide new and important insights into how life arose on Earth.
And then there’s the logic of what finding signs of ancient, or perhaps deep-down surviving life on Mars would mean to the larger search for life in the cosmos.
That life exists on one planet among the hundreds of billions we now know are out there suggests that other planets — which we know have many or most of the same basic chemicals as Earth — might have given rise to life as well.
And if two planets in one of those many, many solar system have produced and supported life, then the odds go up dramatically regarding life on other planets.
One planet with life could be an anomaly. Two nearby planets with life, even if its similar, are a trend.
This blog is being hosted by Knowinnovation Inc. and is supported by the Lunar and Planetary Institute (LPI). LPI is operated by the Universities Space Research Association (USRA) under a cooperative agreement with NASA. The purpose of this blog is to communicate the work of the Nexus for Exoplanet Systems Science (NExSS). Any opinions, findings, and conclusions or recommendations expressed on this blog or its comments are those of the author(s) and do not necessarily reflect the views of NASA.