Technosignatures and the Search for Extraterrestrial Intelligence

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A rendering of a potential Dyson sphere, named after Freeman A. Dyson. As proposed by the physicist and astromomer decades ago, they would collect solar energy on a solar system wide scale for highly advanced civilizations. (SentientDevelopments.com)

The word “SETI” pretty much brings to mind the search for radio signals come from distant planets, the movie “Contact,” Jill Tarter, Frank Drake and perhaps the SETI Institute, where the effort lives and breathes.

But there was a time when SETI — the Search for Extraterrestrial Intelligence — was a significantly broader concept, that brought in other ways to look for intelligent life beyond Earth.

In the late 1950s and early 1960s — a time of great interest in UFOs, flying saucers and the like — scientists not only came up with the idea of searching for distant intelligent life via unnatural radio signals, but also by looking for signs of unexpectedly elevated heat signatures and for optical anomalies in the night sky.

The history of this search has seen many sharp turns, with radio SETI at one time embraced by NASA, subsequently de-funded because of congressional opposition, and then developed into a privately and philanthropically funded project of rigor and breadth at the SETI Institute.  The other modes of SETI went pretty much underground and SETI became synonymous with radio searches for ET life.

But this history may be about to take another sharp turn as some in Congress and NASA have become increasingly interested in what are now called “technosignatures,” potentially detectable signatures and signals of the presence of distant advanced civilizations.  Technosignatures are a subset of the larger and far more mature search for biosignatures — evidence of microbial or other primitive life that might exist on some of the billions of exoplanets we now know exist.

And as a sign of this renewed interest, a technosignatures conference was scheduled by NASA at the request of Congress (and especially retiring Republican Rep. Lamar Smith of Texas.)  The conference took place in Houston late last month, and it was most interesting in terms of the new and increasingly sophisticated ideas being explored by scientists involved with broad-based SETI.

“There has been no SETI conference this big and this good in a very long time,” said Jason Wright, an astrophysicist and professor at Pennsylvania State University and chair of the conference’s science organizing committee.  “We’re trying to rebuild the larger SETI community, and this was a good start.”

 

At this point, the search for technosignatures is often likened to that looking for a needle in a haystack. But what scientists are trying to do is define their haystack, determine its essential characteristics, and learn how to best explore it. (Wiki Commons)

 

During the three day meeting in Houston, scientists and interested private and philanthropic reps. heard talks that ranged from the trials and possibilities of traditional radio SETI to quasi philosophical discussions about what potentially detectable planetary transformations and by-products might be signs of an advanced civilization. (An agenda and videos of the talks are here.)

The subjects ranged from surveying the sky for potential millisecond infrared emissions from distant planets that could be purposeful signals, to how the presence of certain unnatural, pollutant chemicals in an exoplanet atmosphere that could be a sign of civilization.  From the search for thermal signatures coming from megacities or other by-products of technological activity, to the possible presence of “megastructures” built to collect a star’s energy by highly evolved beings.

Michael New is Deputy Associate Administrator for Research within NASA’s Science Mission Directorate. He was initially trained in chemical physics. (NASA)

All but the near infrared SETI are for the distant future — or perhaps are on the science fiction side — but astronomy and the search for distant life do tend to move forward slowly.  Theory and inference most often coming well before observation and detection.

So thinking about the basic questions about what scientists might be looking for, Wright said, is an essential part of the process.

Indeed, it is precisely what Michael New, Deputy Associate Administrator for Research within NASA’s Science Mission Directorate, told the conference. 

He said that he, NASA and Congress wanted the broad sweep of ideas and research out there regarding technosignatures, from the current state of the field to potential near-term findings, and known limitations and possibilities.

“The time is really ripe scientifically for revisiting the ideas of technosignatures and how to search for them,” he said.

He offered the promise of NASA help  (admittedly depending to some extent on what Congress and the administration decide) for research into new surveys, new technologies, data-mining algorithms, theories and modelling to advance the hunt for technosignatures.

 

Crew members aboard the International Space Station took this nighttime photograph of much of the Atlantic coast of the United States. The ability to detect the heat and light from this kind of activity on distant exoplanets does not exist today, but some day it might and could potentially help discover an advanced extraterrestrial civilization. (NASA)

 

Among the several dozen scientists who discussed potential signals to search for were the astronomer Jill Tarter, former director of the Center for SETI Research, Planetary Science Institute astrobiologist David Grinspoon and University of Rochester astrophysicist Adam Frank.  They all looked at the big picture, what artifacts in atmospheres, on surfaces and perhaps in space that advanced civilizations would likely produce by dint of their being “advanced.”

All spoke of the harvesting of energy to perform work as a defining feature of a technological planet, with that “work” describing transportation, construction, manufacturing and more.

Beings that have reached the high level of, in Frank’s words, exo-civilization produce heat, pollutants, changes to their planets and surroundings in the process of doing that work.  And so a detection of highly unusual atmospheric, thermal, surface and orbital conditions could be a signal.

One example mentioned by several speakers is the family of chemical chloroflourohydrocarbons (CFCs,)  which are used as commercial refrigerants, propellants and solvents.

Astronomner Jill Tarter is an iconic figure in the SETI world and led the SETI Institute for 30 years. (AFP)

These CFCs are a hazardous and unnatural pollutant on Earth because they destroy the ozone layer, and they could be doing something similar on an exoplanet.  And as described in the conference, the James Webb Space Telescope — once it’s launch and working — could most likely detect such an atmospheric compound if it’s in high concentration and the project was given sufficient telescope time.

A similar single finding described by Tarter that could be revolutionary is the radioactive isotope tritium, which is a by-product of the nuclear fusion process.  It has a short half-life and so any distant discovery would point to a recent use of nuclear energy (as long as it’s not associated with a recent supernova event, which can also produce tritium.)

But there many other less precise ideas put forward.

Glints on the surface of planets could be the product of technology,  as might be weather on an exoplanet that has been extremely well stabilized, modified planetary orbits and chemical disequilibriums in the atmosphere based on the by-products of life and work.  (These disequilibriums are a well-established feature of biosignature research, but Frank presented the idea of a technosphere which would process energy and create by-products at a greater level than its supporting biosphere.)

Another unlikely but most interesting example of a possible technosignature put forward by Tarter and Grinspoon involved the seven planets of the Trappist-1 solar system, all tidally locked and so lit on only one side.  She said that they could potentially be found to be remarkably similar in their basic structure, alignment and dynamics. As Tarter suggested, this could be a sign of highly advanced solar engineering.

 

Artist rendering of the imagined Trappist-1 solar system that had been terraformed to make the planets similar and habitable.  The system is one of the closest found to our own — about 40 light years.

 

Grinspoon seconded that notion about Trappist-1, but in a somewhat different context.

He has worked a great deal on the question of today’s anthroprocene era — when humans actively change the planet — and he expanded on his thinking about Earth into the galaxies.

Grinspoon said that he had just come back from Japan, where he had visited Hiroshima and its atomic bomb sites, and came away with doubts that we were the “intelligent” civilization we often describe ourselves in SETI terms.  A civilization that may well self destruct — a fate he sees as potentially common throughout the cosmos — might be considered “proto-intelligent,” but not smart enough to keep the civilization going over a long time.

Projecting that into the cosmos, Grinspoon argued that there may well be many such doomed civilizations, and then perhaps a far smaller number of those civilizations that make it through the biological-technological bottleneck that we seem to be facing in the centuries ahead.

These civilizations, which he calls semi-immortal, would develop inherently sustainable methods of continuing, including modifying major climate cycles, developing highly sophisticated radars and other tools for mitigating risks, terraforming nearby planets, and even finding ways to evolve the planet as its place in the habitable zone of its host star becomes threatened by the brightening or dulling of that star.

The trick to trying to find such truly evolved civilizations, he said, would be to look for technosignatures that reflect anomalous stability and not rampant growth. In the larger sense, these civilizations would have integrated themselves into the functioning of the planet, just as oxygen, first primitive and then complex life integrated themselves into the essential systems of Earth.

And returning to the technological civilizations that don’t survive, they could produce physical artifacts that now permeate the galaxy.

 

MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas now being tested and verified in the Northern Cape of South Africa. When fully functional it will be the largest and most sensitive radio telescope in the southern hemisphere until the Square Kilometre Array is completed in approximately 2024. (South African Radio Astronomy Observatory)

 

This is exciting – the next phase Square kilometer Array (SKA2) will be able to detect Earth-level radio leakage from nearby stars. (South African Radio Astronomy Observatory)

 

While the conference focused on technosignature theory, models, and distant possibilities, news was also shared about two concrete developments involving research today.

The first involved the radio telescope array in South Africa now called MeerKAT,  a prototype of sorts that will eventually become the gigantic Square Kilometer Array.

Breakthrough Listen, the global initiative to seek signs of intelligent life in the universe, would soon announce the commencement of  a major new program with the MeerKAT telescope, in partnership with the South African Radio Astronomy Observatory (SARAO).

Breakthrough Listen’s MeerKAT survey will examine a million individual stars – 1,000 times the number of targets in any previous search – in the quietest part of the radio spectrum, monitoring for signs of extraterrestrial technology. With the addition of MeerKAT’s observations to its existing surveys, Listen will operate 24 hours a day, seven days a week, in parallel with other surveys.

This clearly has the possibility of greatly expanded the amount of SETI listening being done.  The SETI Institute, with its radio astronomy array in northern California and various partners, have been listening for almost 60 years, without detecting a signal from our galaxy.

That might seem like a disappointing intimation that nothing or nobody else is out there, but not if you listen to Tarter explain how much listening has actually been done.  Almost ten years ago, she calculated that if the Milky Way galaxy and everything in it was an ocean, then SETI would have listened to a cup full of water from that ocean.  Jason Wright and his students did an updated calculation recently, and now the radio listening amounts to a small swimming pool within that enormous ocean.

 

The NIROSETI team with their new infrared detector inside the dome at Lick Observatory. Left to right: Remington Stone, Dan Wertheimer, Jérome Maire, Shelley Wright, Patrick Dorval and Richard Treffers. (Laurie Hatch)

The other news came from Shelley Wright of the University of California, San Diego, who has been working on an optical SETI instrument for the Lick Observatory.

The Near-Infrared Optical SETI (NIROSETI) instrument she and her colleagues have developed is the first instrument of its kind designed to search for signals from extraterrestrials at near-Infrared wavelengths. The near-infrared regime is an excellenr spectral region to search for signals from extraterrestrials, since it offers a unique window for interstellar communication.

The NIROSETI instrument utilizes two near-infrared photodiodes to be able to detect artificial, very fast (nanosecond) pulses of infrared radiation.

The NIROSETI instrument, which is mounted on the Nickel telescope at Lick Observatory, splits the incoming near-infrared light onto two channels, and then checks for coincident events, which indicate signals that are identified by both detectors simultaneously.

Jason Wright is an assistant professor of astronomy and astrophysics at Penn State. His reading list is here.

Wright of Penn State was especially impressed by the project, which he said can look at much of the sky at once and was put together with on very limited budget.

Wright, who teaches a course on SETI at Penn State and is a co-author of a recent paper trying to formalize SETI terminology, said his own take-away from the conference is that it may well represent an important and positive moment in the history of technosignatures.

“Without NASA support, the whole field has lacked the normal structure by which astronomy advances,” he said.  “No teaching of the subject, no standard terms, no textbook to formalize findings and understandings.

“The Seti Institiute carried us through the dark times, and they did that outside of normal, formal structures. The Institute remains essential, but hopefully that reflex identification will start to change.”

 

Participants in the technosignatures conference in Houston last month, the largest SETI gathering in years.  And this one was sponsored by NASA and put together by the NExSS for Exoplanet Systems Science (NExSS,)  an interdisciplinary agency initiative. (Delia Enriquez)
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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Human Space Travel, Health and Risk

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Astronauts in a mock-up of the Orion space capsule, which NASA plans to use in some form as a deep-space vehicle. (NASA)

 

We all know that human space travel is risky. Always has been and always will be.

Imagine, for a second, that you’re an astronaut about to be sent on a journey to Mars and back, and you’re in a capsule on top of NASA’s second-generation Space Launch System designed for that task.

You will be 384 feet in the air waiting to launch (as tall as a 38-floor building,) the rocket system will weigh 6.5 million pounds (equivalent to almost nine fully-loaded 747 jets) and you will take off with 9.2 million pounds of thrust (34 times the total thrust of one of those 747s.)

Given the thrill and power of such a launch and later descent, everything else seemed to pale in terms of both drama and riskiness.  But as NASA has been learning more and more, the risks continue in space and perhaps even increase.

We’re not talking here about a leak or a malfunction computer system; we’re talking about absolutely inevitable risks from cosmic rays and radiation generally — as well as from micro-gravity — during a long journey in space.

Since no human has been in deep space for more than a short time, the task of understanding those health risks is very tricky and utterly dependent on testing creatures other than humans.

The most recent results are sobering.  A NASA-sponsored team at Georgetown University Medical Center in Washington looked specifically at what could happen to a human digestive system on a long Martian venture, and the results were not reassuring.

Their results, published in the Proceedings of the National Academy of Sciences  (PNAS), suggests that deep space bombardment by galactic cosmic radiation and solar particles could significantly damage gastrointestinal tissue leading to long-term functional changes and problems. The study also raises concern about high risk of tumor development in the stomach and colon.

 

Galactic cosmic rays are a variable shower of charged particles coming from supernova explosions and other events extremely far from our solar system. The sun is the other main source of energetic particles this investigation detects and characterizes. The sun spews electrons, protons and heavier ions in “solar particle events” fed by solar flares and ejections of matter from the sun’s corona. Magnetic fields around Earth protect the planet from most of these heavy particles, but astronauts do not have that protect beyond low-Earth orbit. (NASA)

 

Kamal Datta, an associate professor in the Department of Biochemistry is project leader of the NASA Specialized Center of Research (NSCOR) at Georgetown and has been studying the effects of space radiation on humans for more than a decade.

He said that heavy ions (electrically charged atoms and molecules) of elements such as iron and silicon are damaging to humans because of their greater mass compared to mass-less photons such as x-rays and gamma rays prevalent on Earth.  These heavy ions, as well as low mass protons, are ubiquitous in deep space.

Kamal Datta of Georgetown University Medical Center works with NASA to understand the potential risks from galactic cosmic radiation to astronauts who may one day travel in deep space.

“With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation. Although there may be a way to use medicines to counter these effects, no such agent has been developed yet,” says Datta, also a member of Georgetown Lombardi Comprehensive Cancer Center.

“While short trips, like the times astronauts traveled to the moon, may not expose them to this level of damage, the real concern is lasting injury from a long trip, such as a Mars or other deep space missions which would be much longer” he said in a release.

Datta’s team has also published on the potentially harmful effects of galactic cosmic radiation on the brain and other teams are looking at potential deep-space travel dangers the human cardio-vascular system.  Researchers are also concerned about known weakening of bone and muscle tissue, harming vision, as well as speeded-up aging during long stays in space.

With current technology, it would take about three years to travel from Earth to Mars, orbit the planet until it is in the right place for a sling-shot boost home, and then to travel back.

A radiation detection instrument on the Mars Science Laboratory (MSL),  which carried the rover Curiosity to Mars in 2011-2012, measured an estimated overall human radiation exposure for a Mars trip that would would be two-thirds of the agency’s allowed lifetime limits.  That was based on the high-energy radiation hitting the capsule, but NASA later detected radiation bursts from solar flares on Mars far higher than anything detected during the MSL transit.

All of this seems, and is, quite daunting when thinking about human travel to Mars and other deep space destinations.  And Datta is clearly sensitive about how the new results are conveyed to the public.

“I am in no way saying that people cannot travel to Mars,” he told me. “What we are doing is trying to understand the health risks so proper mitigation can be devised, not to say this kind of travel is impossible.”

“We don’t have medicines now to protect astronauts from heavy particle radiation, and we don’t have the technology now to shield them while they’re in space.  But many people are working on these problems.”

 

The Orion spacecraft in flight, as drawn by an artist. The capsule has an attached habitat module. (NASA)

 

On the medical research side, scientists have to rely on data gained from exposing mice to radiation and extrapolating those results to humans.  It would, of course, be unethical to do the testing on people.

While this kind of animal testing is accepted as generally accurate, it certainly could hide either increased protections or increased risks in humans.

Datta said that another testing issue that has been present so far is that the mice have had to be irradiated in one large dose rather than in much smaller doses over time.  It is unclear how that effects the potential damage to human organs and the breaking of DNA bonds (which can result in the growth of cancers.)  But Datta said that new instruments at NASA’s Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory on Long Island, New York, will allow for a more gradual, lower-dose experiment.

While Datta’s work has been focused on the health risks of deep space travel, galactic cosmic radiation and solar heavy particles also bombard the moon — which has no magnetic field and only a very thin atmosphere to protect it.  Apollo astronauts could safely stay on the moon for several days in their suits and their lander, but months or years of living in a colony there would pose far greater risks.

NASA has actually funded projects to shield small areas on the moon from radiation, but the issue remains very much unresolved.

Shielding also plays a major role in thinking about how to protect astronauts traveling into deep space.  The current aluminum skin of space capsules allows much of the harmful radiation to pass through, and so something is needed to block it.

 

The goal of building an inhabited colony on the moon has many avid supporters in government and the private sector. The health risks for astronauts are similar to those in deep space. (NASA/Pat Rawlings)

 

Experts have concluded that perhaps the best barrier to radiation would be a layer of water, but it is too heavy to carry in the needed amounts.  Other possibilities include organic polymers (large macromolecules with repeating subunits) such as polyethelyne.

It seems clear that issues such as these — the effects of more hazardous space radiation on astronauts in deep space and on the moon, and how to minimize those dangers — will be coming to the front burner in the years ahead.  And assuming that progress can be made, it’s a thrilling time.

What this means for space science, however, is less clear.

On one hand I recall hearing former astronaut extraordinaire and then head of the NASA Science Mission Directorate John Grunsfeld talk about how an astronaut on Mars could gather data and understandings in one week that the Curiosity rover would need a full year to match.

On the other, human space exploration is much more expensive than anything without people — yes, even including the long-delayed and ever-more-costly James Webb Space Telescope — and NASA budgets are limited.

So the question arises whether human exploration will, when it gets into high gear, swallow up the resources needed for the successors to the Hubble, Curiosity, Cassini and the other missions that have helped create what I consider to be a golden age of space science.  Risks come in many forms.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Time-Traveling in the Australian Outback in Search of Early Earth

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This story was written by Nicholas Siegler, Chief Technologist for NASA’s Exoplanet Exploration Program at the Jet Propulsion Laboratory with the help of doctoral student Markus Gogouvitis, at the University of New South Wales, Australia and Georg-August-University in Gottingen, Germany.

 

These living stromatolites at Shark Bay, Australia are descendants of similar microbial/sedimentary forms once common around the world.  They are among the oldest known repositories of life.  Most stromatolites died off long ago, but remain at Shark Bay because of the high salinity of the water. (Tourism, Western Australia)

 

This past July I joined a group of geologists, geochemists, microbiologists, and fellow astronomers on a tour of some of the best-preserved evidence for early life.

Entitled the Astrobiology Grand Tour, it was a trip led by Dr. Martin Van Kranendonk, a structural geologist from the University of New South Wales, who had spent more than 25 years surveying Australia’s Pilbara region. Along with his graduate students he had organized a ten-day excursion deep into the outback of Western Australia to visit some of astrobiology’s most renowned sites.

The trip would entail long, hot days of hiking through unmaintained trails on loose surface rocks covered by barb-like bushes called spinifex.  As I was to find out, nature was not going to give up its secrets easily.  And there were no special privileges allocated to astrophysicists from New Jersey.

 

The route of our journey back in time.  (Google Earth/Markus Gogouvitis /Martin Van Kranendonk)

The state of Western Australia, almost four times the size of the American state of Texas but with less than a tenth of the population (2.6 million), is the site of many of astrobiology’s most heralded sites. For more than three billion years, it has been one of the most stable geologic regions in the world.

It has been ideal for geological preservation due to its arid conditions, lack of tectonic movement, and remoteness. The rock records have in many places survived and are now able to tell their stories (to those who know how to listen).

 

The classic red rocks of the Pilbara in Western Australia, with the needle sharp spinifex bushes in the foreground. (Nick Siegler, NASA/JPL-Caltech)

Our trip began with what felt like a pilgrimage. We left Western Australia’s largest city Perth and headed north for Shark bsy. It felt a bit like a pilgrimage because the next morning we visited one of modern astrobiology’s highlights – the living stromatolites of Shark Bay.

Stromatolites literally mean “layered rocks”. It’s not the rocks that are alive but rather the community of microbial mats living on top. They are some of the Earth’s earliest ecosystems.

We gazed over these living microbial communities aloft on their rock perches and marveled at their exceptional longevity — the species has persisted for over three billion years. Their ancestors had survived global mass extinctions, planet-covering ice glaciers, volcanic activity, and all sorts of predators. Once these life forms took hold they were not going to let go.

 

The stromatolites forming today in the shallow waters of Shark Bay, Australia are built by colonies of microbes that capture ocean sediments. (University of Wisconsin-Madison)

The photosynthetic bacteria that built ancient stromatolites played a central role of our trip for three reasons:

  • Their geological footprints allowed scientists to date the evolution of early life and at times gain insight into the environments in which they grew.
  • They eventually harbored the first oxygen-producing bacteria and played a central role in creating our oxygen-rich atmosphere.
  • By locating ever-increasingly older microbial fossils we observed a lower limit to the age of the first life forms.. Given photosynthesis is not a simple process, the first life forms must have been simpler. Speculating, perhaps a few hundred million years earlier so that the first life form on Earth may have originated at four billion years ago.

When viewed under a microscope, you can see the mats are made of millions of single cell bacteria and archaea, among the simplest life forms we know. Within these relatively thin regions are multiple layers of specialized microbial communities that live interdependently.

Bacteria in the top layer evolved to harvest sunlight to live and grow via photosynthesis. Their waste products include oxygen as well as important nutrients for many different bacterial species within underlying layers. And this underlying layer’s waste product would do the same for the layer beneath it, perfectly recycling each other’s waste. The oldest forms of life that we know of had learned to co-exist together in a chemically interdependent environment.

 

Broken piece of a living stromatolite, which was was remarkably spongy and smelled slightly salty, indicative of the hypersaline bay that has contributed to their survival by making bacteria and other organisms undesirable. What was actually most remarkable of the visit to Hamelin pool was how quiet it was. There were no seagulls and other birds because of the hypersaline environment. They had gone elsewhere for their meals. (Nick Siegler, NASA/JPL-Caltech)

 

We saw ripped up portions of the mats that washed upon the shore at Hamelin pool in Shark Bay. A whole ecosystem held in one’s hand. Thousands of millions of years ago ancient relatives of these microbes thrived in shallow waters all around our planet, and left behind fossilized remains. But due to the evolution of grazing organisms these microbial structures are nowadays constrained to very specific environments. In the case of Shark Bay, the very high salt contents of this inlet have warded off most predators providing the microbes with a safe haven to live.

Ironically, the rocks, which help identify these ancient life forms, at the time were just a nuisance for the living microbes.

Small fine grains of sedimentary rock carried along in the daily tides would occasionally get stuck in the sticky mucus the microbes would secrete. In addition, the photosynthetic bacteria found at Shark Bay may have been inadvertently making their own rock by depleting the carbon dioxide in the surrounding water as part of photosynthesis and precipitating carbonate, adding to the grains of sediment trapped within the sticky top layer.

Over time, the grains from both the sedimentary and precipitated rocks would  cover the surface and block the sunlight for which these organisms had evolved to depend on. As an evolutionary tour de force, the photosynthetic microbes learned to migrate upward, leaving the newly formed rock layers behind.

These secondary rock fossils today showcase visually observable crinkly, frequently conical shapes, in stark contrast to abiotic sedimentary rocks. These ancient life forms left behind geological footprints reminding us they were here first.

Nick Siegler of JPL on his Australian Magical Origins Tour.  (Markus Gogouvitis)

Now to the most important contribution of stromatolites – terraforming the Earth.

Living in shallow water, the top most layer of the Shark Bay microbial mats are known to host cyanobacteria, photosynthetic bacteria that produce oxygen as a byproduct. Scientists don’t know what the first bacteria produced as they harnessed the energy of the Sun. But they do know that they eventually started producing oxygen.

In the evolution of life that eventually led to all plants and animals, this was one of the great events. More than 2.5 billion years ago, ancient bacteria began diligently producing oxygen in the oceans. Earth’s atmosphere began to irreversibly shift from its original, oxygen-free existence, to an oxic one, initiating the formation of our ozone layer and paving the way for the evolution of more complex life. Our planet has been terraformed by micro-organisms!

It was in the Karijini National Park where we went back in time (2.4 billion years) and observed an extraordinary piece of evidence for the early production of oxygen in Earth’s oceans, a time before oxygen made a strong presence in our atmosphere.

 

Banded iron formation at Karajini National Park.  (Nick Siegler, NASA-JPL/Caltech)

 

We saw a massive gorge with steep vertical walls carved out by flowing water. As oxygen production by early bacteria increased below the water surface it would react with dissolved iron ions (early oceans were iron-rich) causing iron oxides to precipitate and settle to the bottom.

For reasons not entirely understood — perhaps related to seasonal or temperature effects– the amount of new oxygen temporarily decreased and iron ion remained soluble in the oceans and other types of sediments accumulated, carbonates, slate, and shale. And then, just as before, the oxygen reappeared creating a new layer of precipitated iron.

The result was a banded sedimentary rock, a litmus test to a changing world, where oxygen would be the reactive ingredient leading to larger and more complex life forms. As the oxygen production no longer cycled, the oxygen went on to saturate the ocean and then accumulated in the Earth’s atmosphere eventually to the levels we have today.

 

Banded iron formation at Karajini. (Nick Siegler, NASA-JPL/Caltech)

After a day of looking down at rocks and spinifex it was both a relief and a joy to look up at the glorious Western Australian night sky. Far away from the light pollution of modern cities, each night would greet us with an awe-inspiring starlit sky. It never got old to remember we are part of a vast network of stars suspended in an infinite space.

The nights would start with the appearance of Venus well before sundown followed shortly by the innermost planet Mercury and then Jupiter and Saturn. It didn’t take long after sunset to see the renowned Southern Cross. Mars joined the evening as well, perfectly appearing on the arc called the ecliptic.

But nothing stirred the group more than the emergence of the swath of stars of the Milky Way, the disk of our home galaxy where its spiral arms all lie. The nights would be so clear that one could actually see the dark clouds of gas and dust that block large portions of the galaxy’s stars from shining through. We partook in the well-known tradition connecting individual points of light to form exotic creatures like scorpions and centaurs. But we also we followed the inverted approach of the Aborigines and connected the dark patches. Only then did we see the emu of the Milky Way. I would never have thought of connecting the darkness.

 

Australian night sky, with campfire below.  (Maëva Millan/NASA-GSFC/Georgetown University)

The night sky appeared even more special knowing that each of its stellar members likely host planetary systems like our own. How many of them host life? Maybe even civilizations? The numbers are in their favor.

At the half-way point of our trip we hiked to an ancient granite region in the red rocks of the Pilbara which contain the world’s largest concentration of Pleistocene rock art also known as petroglyphs. These etchings are believed to be 6,000 to 20, 000 years old.

The artists used no pigments, but rather rocks to pound/chisel shapes into the desert varnish, a thin dark film (possibly of microbial origin) that typically covers exposed rock surfaces in hyper arid regions. We came across many stylized male and female figures with highlighted genitalia as well as animals such as emus and kangaroos. Little is known about the people who created these art works. They left no clues to their origin or fate.

 

Rock art by aboriginal people done 6,000 to 20,000 years ago. The shapes were etched into an existing varnish on the rock. (Nick Siegler, NASA-JPL/Caltech)

Pilbara is also where the oldest mineral on Earth –a zircon dated at 4.4 billion years old — was discovered four years ago in the Jack Hills region.  Because of the geological history of the region, it is a frequent (if hardscrabble) site where many geologists and geochemists specializing in ancient Earth do their work.

In the last several days of the tour we encountered ever-increasing older evidence of stromatolites extending out to circa 3.5 billion years, about 75% of the history of the Earth. I expected the quality of the stromatolites to degrade as we went back in time and it looked like I was right until I saw a remarkably large rock in a locality called the Strelley Pool Formation. The rock measuring approximately 1.5 meters in all three directions gave a rare view of ancient stromatolites from all sides and an unequivocal interpretation of past life.

Large and ancient fossil stromatolite at the Strelley Pool Formation, with Siegler and Gogouvitis.  (Nick Siegler, NASA-JPL/Caltech)

The shapes of the embedded rocks formed by the microbial mats from the top view clearly show the elliptical areas where the bacteria inched upwards to acquire sunlight. Regions between the conical stromatolites were filled in by carbonate sediments in ancient shallow waters. These were later chemically altered to silica-rich rocks through alteration and etching of minerals by fluids. Silicified rocks are very weather-resistant, making them a great medium to preserve fossils for billions of years.

The side views of the stromatolite-laden rock revealed the expected conical layered shapes we saw in younger rocks (and in the living stromatolites of Shark Bay). Everything we had learned about stromatolite structures was clearly visible in this circa 3.43 billion year old example. It is astounding to realize that complex phototrophic (light-eating) organisms, even if not yet oxygen producing, were around during the deposition of the Strelley Pool Formation.

 

Detail of Strelley Pool stromatolite fossil.  (Nick Siegler, NASA-JPL/Caltech)

It is not unreasonable to speculate that the earliest life forms are even older by perhaps a few more hundred million years or so. There is evidence for even more ancient stromatolites in Greenland (3.7 billion years old) and isotope carbon evidence, with considerable controversy, in Nuvvuagittuq greenstone belt in northern Quebec, Canada (4.28 billion years old). Hence, life on Earth may have emerged within 500 million years from its formation. That is astonishingly rapid.

Was Earth an exception or the rule? What does that say for possible life on exoplanets?

Our tour came to an end on July 11. We had traveled over 1,600 miles through Australia’s outback, from Western Australia’s biggest city Perth, all the way up to Port Hedland at the north coast. We were privileged to see the country in ways that very few people get a chance to, and to be steeped in the multidisciplinary sciences of astrobiology while seeing some of its iconic ground.

I had seen some of the earliest evidence for life and the pivotal effect it had on our environment. For those 10 days I learned what it was like to be a time traveler.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Water Worlds, Aquaplanets and Habitability

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This artist rendering may show a water world — without any land — or an aquaplanet with lots of more shallow water around a rocky planet. (NASA)

 

The more exoplanet scientists learn about the billions and billions of celestial bodies out there, the more the question of unusual planets — those with characteristics quite different from those in our solar system — has come into play.

Hot Jupiters, super-Earths, planets orbiting much smaller red dwarf stars — they are all grist for the exoplanet mill, for scientists trying to understand the planetary world that has exploded with possibilities and puzzles over the past two decades.

Another important category of planets unlike those we know are the loosely called “water worlds” (with very deep oceans) and their “aquaplanet” cousins (with a covering of water and continents) but orbiting stars very much unlike our sun.

Two recent papers address the central question of habitability in terms of these kind of planets — one with oceans and ice hundreds of miles deep, and one particular and compelling planet (Proxima Centauri b, the exoplanet closest to us) hypothesized to have water on its surface as it orbits a red dwarf star.

The question the papers address is whether these watery worlds might be habitable.  The conclusions are based on modelling rather than observations, and they are both compelling and surprising.

In both cases — a planet with liquid H20 and ice many miles down, and another that probably faces its red dwarf sun all or most of the time — the answers from modelers is that yes, the planets could be habitable.   That is very different from saying they are or even might be inhabited.  Rather,  the conclusions are based on computer models that take into account myriad conditions and come out with simulations about what kind of planets they might be.

This finding of potential watery-world habitability is no small matter because predictions of how planets form point to an abundance of water and ice in the planetesimals that grow into planets.

As described by Eric Ford, co-author of one of the papers and a professor of astrophysics at Pennsylvania State University, “Many scientists anticipate that planets with oceans much deeper than Earths could be a common outcome of planet formation. Indeed, one of the puzzling properties of Earth is that it has oceans that are just skin deep” compared to the radius of the planet.

“While some planets very close to their star might loose all their water, it would take a delicate balancing act to remove many ocean’s worth of water and to leave a planet with oceans as shallow as those on Earth.”

An interesting place to start.

 

Artist’s conception of a planet covered with a global ocean. A new study finds that these wate rworlds could maintain stable climates and perhaps sustain life under certain conditions. (ESO/M. Kornmesser)

 

It should first be said that many scientists are dubious that extreme water worlds can support life or can support detectable life.  My colleague Elizabeth Tasker wrote a column — Can You Overwater a Planet? — focused on this view last year.

The first of the two new exoplanets/ocean papers involves planets with very deep oceans. Written by Edwin Kite of the University of Chicago and Ford of Penn State, the paper in the Astrophysical Journal concludes that even a planet with such super deep oceans could — under certain conditions — provide habitable conditions.

This finding is at odds with previous simulations, and Kite says that is part of its significance. The scientific community has largely assumed that planets covered in a deep ocean would not support the cycling of minerals and gases that keeps the climate stable on Earth, and thus wouldn’t be friendly to life.

But the Kite and Ford study found that ocean planets (with 10 to 1000 times as much water as Earth) could remain habitable much longer than previously assumed. The authors performed more than a thousand simulations to reach that conclusion.

Eric Ford is a professor astrophysics at Penn State and a specialist in planet formation. (Penn State)

“This really pushes back against the idea you need an Earth clone—that is, a planet with some land and a shallow ocean,” said Edwin Kite, assistant professor of geophysical sciences at the University of Chicago and lead author of the study.

Edwin Kite is an assistant professor of planetary sciences at the University of Chicago. (Univ. of Chicago)

Because life needs an extended period to evolve — and because the light and heat on planets can change as their stars age — scientists usually look for planets that have both some water and some way to keep their climates stable over time. The method for achieving this steady state that we know is, of course, how it works on Earth. Over eons, our planet has cooled itself by drawing down atmospheric greenhouse gases into minerals and warms itself up by releasing them via volcanoes.

But this model doesn’t work on a water world, with deep water covering the rock and suppressing volcanoes.

Kite and Ford wanted to know if there was another way to achieve a balance. They set up a simulation with thousands of randomly generated planets, and tracked the evolution of their climates over billions of years.

“The surprise was that many of them stay stable for more than a billion years, just by luck of the draw,” Kite said. “Our best guess is that it’s on the order of 10 percent of them.”

These planets sit in the right location around their stars. They happened to have the right amount of carbon present, and they don’t have too many minerals and elements from the crust dissolved in the oceans that would pull carbon out of the atmosphere. They have enough water from the start, and they cycle carbon between the atmosphere and ocean only, which in the right concentrations is sufficient to keep things stable.

None of this means that such a planet exists — our ability to detect oceans worlds is in its infancy.  The issue is rather that Kite and Ford conclude that a deep ocean planet could potentially be habitable if other conditions were met.

 

Artist rendering of Proxima Centauri b orbiting its red dwarf host star. (ESO/L.Calçada/Nick Risinger)

 

Anthony Del Genio and his team of modelers at NASA’s Goddard Institute for Space Studies in New York used their state-of-the-art climate simulations to look at another aspect of the exoplanet water story, and they chose Proxima Centauri b as their subject.  The roughly Earth-sized planet was discovered in 2016 and is the closest exoplanet to Earth.

Scientists determined early on that it is a rocky (as opposed to gaseous) planet and that it orbits its host star every 11 days.  If that star was as powerful as our sun, there would be no talk of possible habitability on close-in Proxima b.  But the star is a red dwarf and puts out only a fraction of the radiation coming from a host star like our sun.

Still, the case for habitability on Proxima b was initially considered to be weak, in part because the planet is tidally locked by its closeness to the host star.  In other words, it would most likely not spin to create days and nights as it orbits, but rather would have a sun-facing side and a space-facing side — making the temperature differences great.

Our ability to characterize a small planet like Proxima b remains very limited, and so it is unknown whether the planet has water or whether it has an atmosphere.  So those two essential components of the habitability question are missing.

But Del Genio’s team decided to model the dynamics of Proxima b with a presumed ocean, though not one that is many miles deep.  In Earth science parlance, what Del Genio referred to as an “aquaplanet.” And using their sophisticated models, they would simulate “dynamic” oceans with currents like our own, rather than the stationary oceans modeled earlier on exoplanets.

And rather to their surprise, they reported in the journal Astrobiology that their model of ocean behavior showed that the planet would not have only small areas of potential habitability — the earlier proposed habitable “eyeball” scenario — but rather much of the planet could be habitable.  That could include some of the normally space-facing side.

 

One type of possible water world is an “eyeball” planet, where the star-facing side is able to maintain a liquid-water ocean, while the rest of the surface is ice. (Image via eburacum45/DeviantArt)

 

“Our group said let’s hook up an atmosphere to a dynamic ocean rather than a static one,” Del Genio said.  “That way you get ocean currents like those on our coasts, and they move water of different temperatures around.

“If you have a real and dynamic ocean in your model, then we found that the eyeball goes away.  Usually the currents go west to east and they carry warmer water even to the night side.”

Anthony Del Genio, leader of NASA’s GISS team that  uses cutting edge Earth climate models to better understand conditions on exoplanets.

So using this more sophisticated model, not insignificant areas of Proxima b, or any other planet like it orbiting a red dwarf star, could be habitable, they concluded.  But again, that is assuming some pretty big “ifs” — the presence of an ocean and an atmosphere.

And then the team added variables such as a thick nitrogen and carbon atmosphere or a thin one, fresh water or salty water, a planet that is firmly locked and never rotating, or one that rotates a modest amount — giving the dark side some light.  Del Genio said that with all these added factors, a substantial portion of the surface of Proxima b, or a planet like it, would have liquid water and potentially habitable conditions.

This focus on watery worlds — including those that would be extreme compared with Earth today — makes sense in the context of the history of Earth.

While there is no direct evidence of this, many scientists think that the very early Earth was covered for a period of time with water with little or no land.

And then after land appeared, it still took some three billion years for any life form — bacteria, early planets — to colonize the land, and another half billion years for animals to come ashore.  Yet the oceans were long habitable and inhabited, as early a 3.8 billion years ago.

So until astronomy and exoplanet science develop the needed instruments and scientists acquire the observed knowledge of conditions on water worlds, progress will come largely from modelling that tells us what might be possible.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Curiosity Rover Looks Around Full Circle And Sees A Once Habitable World Through The Dust

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An annotated 360-degree view from the Curiosity mast camera.  Dust remaining from an enormous recent storm can be seen on the platform and in the sky.  And holes in the tires speak of the rough terrain Curiosity has traveled, but now avoids whenever possible. Make the screen bigger for best results and enjoy the show. (NASA/JPL-Caltech/MSSS)

 

When it comes to the search for life beyond Earth, I think it would be hard to point to a body more captivating, and certainly more studied, than Mars.

The Curiosity rover team concluded fairly early in its six-year mission on the planet that “habitable” conditions existed on early Mars.  That finding came from the indisputable presence of substantial amounts of liquid water three-billion-plus years ago, of oxidizing and reducing molecules that could provide energy for simple life, of organic compounds and of an atmosphere that was thick enough to block some of the most harmful incoming cosmic rays.

Last year, Curiosity scientists estimated that the window for a habitable Mars was some 700 million years, from 3.8 to 3.1 billion years ago.  Is it a coincidence that the earliest confirmed life on Earth appeared about 3.8 billion years ago?

Today’s frigid Mars, which has an atmosphere much thinner than in the planet’s early days, hardly looks inviting, although some scientists do see a possibility that primitive life survives below the surface.

But because it doesn’t look inviting now doesn’t mean the signs of a very different planet aren’t visible and detectable through instruments.  The Curiosity mission has proven this once and for all.

The just released and compelling 360-degree look (above) at the area including Vera Rubin Ridge brings the message home.

Those fractured, flat rocks are mudstone, formed when Gale Crater was home to Gale Lake.  Mudstone and other sedimentary formations have been visible (and sometimes drilled) along a fair amount of the 12.26-mile path that Curiosity has traveled since touchdown.

 

An image of Vera Rubin Ridge in traditional Curiosity color, and the same view below with filters designed to detect hematite, or iron oxide. That compound can only be formed in the presence of water. (NASA/JPL-Caltech)

 

The area the rover is now exploring contains enough hematite — iron oxide — that its signal was detectable from far above the planet, making this area a prized destination since well before the Mars Science Laboratory and Curiosity were launched.

Like Martian clays and sulfates that have been identified and explored, the hematite is of great interest because of its origins in water.  Without H2O present many eons ago, there would be no hematite, no clay, no sulfates.  But as Mars researchers have found, there is a lot of all three.

I like to return to Mars and especially Curiosity because it provides something unique in the cosmos:  an environment where scientists today have ground-truthed the hypothesis that early Mars was once habitable, and found unambiguous results that it was.

That doesn’t mean that the planet necessarily ever gave rise to, or supported, living organisms.  But it’s a lot more than can be said for other targets for life beyond Earth.

NASA’s Europa Clipper may determine some day that beneath the ice crust of that moon of Jupiter is an ocean that is, or was, habitable.  But that determination is still years away.  Same with Saturn’s moon Enceladus, which some see as habitable beneath its ice, but no mission is currently approved to determine that.

And when it comes to exoplanets and possible life on them, it is both a logical and alluring conclusion that some support living organisms — there are, after all, billions and billions of exoplanets, and the cosmos is filled with the elements and compounds we find on Earth.

But we remain quite far away from consensus on what an exoplanet biosignature might be, and much further away from being able to confidently detect the probable biosignature elements and compounds on distant exoplanets.

And so for now we have Mars as our most plausible target for life beyond Earth.

 

Vera Rubin Ridge, with its high concentration of both red and green hematite. (NASA/JPL-Caltech)

 

It wasn’t that long ago that the NASA exploration mantra for Mars was “follow the water,”  under the assumption that life needed water to survive.

But Curiosity and satellites orbiting Mars have found abundant proof that water did play a major role in the planet’s early times.  Not only has Curiosity found that a lake existed on and off for hundreds of millions of years at Gale Crater, but researchers recently announced the presence of a large reservoir of liquid water beneath the southern polar region.

What’s more, evidence of briny surface streams on steep Martian cliffs in their warm season has grown stronger, though it remains a much-debated finding.

But with the water story well established, researchers are focused more on organics, minerals and what can be found beneath the radiation-baked surface.

Curiosity has been working for months around Vera Rubin Ridge, though for much of that time with a big handicap — the rover’s long-armed drill wasn’t working.  Important internal mechanisms stopped performing in late 2016, and it wasn’t until late spring of 2018 that a workaround was ready.

After one successful drilling, the next two failed.  But there was no drill problem with those two; the rock on the ridge was just too hard to penetrate.  It makes sense that the rock would be very hard because it has withstood millions of years of powerful winds blowing across Gale Crater, while other nearby rock and sediments were carried away.

The best way to discover why these rocks are so hard is to drill them into a powder for the rover’s two internal laboratories. Analyzing them might reveal what’s acting as “cement” in the ridge, enabling it to stand despite wind erosion.

Most likely, said Curiosity project scientist Ashin Vasavada, groundwater flowing through the ridge in the ancient past had a role in strengthening it, perhaps acting as plumbing to distribute this wind-proofing “cement.” In this case, it would be some variation of hematite, which in crystal form can be pretty hard on its own.

On its third attempt — and after a prolonged search for a “soft” spot in the ridge — the Curiosity drill did succeed in digging a hole and bringing back some precious powdered contents for study in the two onboard labs.

After the exploration of Vera Rubin Ridge and its hematite will come explorations of large deposits of sulfates and phyllosilicates (clays) — both formed in water as well — further up Mt. Sharp.

 

Curiosity’s pathway over the past six years, from near the Bradbury Landing site to the successful drilling at Vera Rubin Ridge. The route has gone through fossil lake beds, dune fields, the underlying rock formation of Mt. Sharp and now up to the hematite concentrations. (NASA/JPL=Calgtech)

 

I find the landscape of Mars that Curiosity shows us to be captivating, but also sobering when it comes to the search for life beyond Earth.

Here is the planet closest to Earth (during some orbits, at least), one that has been determined to be habitable 3 to 4 billion years ago,  one that can be studied with rovers on the ground and orbiting satellites — and still we can’t determine if it ever actually supported life, and probably won’t be able to for decades to come.

The big confounding factor on Mars really is time.  Life could have come and gone billions of years ago, and intense surface radiation could have erased that history and made it appear as if life was never there.  (This is one reason why Mars scientists want to dig deeper below the surface, where the effects of radiation would be much reduced.)

Time may be a powerful obstacle when it comes finding signs of life on exoplanets as well.  If life exists elsewhere in the cosmos, it surely comes and goes, too.  The odds of us catching it when it’s present may be low, despite all those billions and billions of planets. (Given the way that exoplanet biosignatures work, the life needs to be present at the time of observation.)

Or maybe the time for life in the cosmos has really just begun.

Harvard-Smithsonian astrophysicist Avi Loeb argued several years ago that life on Earth may be a premature flowering, compared with what may well happen later and elsewhere. (Column on his intriguing ideas is here.)

A majority of stars in the cosmos are red dwarfs, or M stars.  They take eons to stabilize and then generally continue in a steady state for much longer than a G star like our sun.  So, he argued,  life in the cosmos around red dwarfs may not become widespread for some time, and then could last for a very long time if and when it did arise.

But enough about time — other than to perhaps take a little more time to enjoy the 360-degree view of Mars and Curiosity that brings thoughts like these to mind.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.