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


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.



Curiosity Has Found The Element Boron On Mars. That’s More Important Than You Might Think

ChemCam target Catabola is a raised resistant calcium sulfate vein with the highest abundance of boron observed so far. The red outline shows the location of the ChemCam target remote micro images (inset). The remote micro images show the location of each individual ChemCam laser point (red crosshairs) and the B chemistry associated with each point (colored bars). The scale bar is 9.2 mm or about 0.36 inches. Credit JPL-Caltech/MSSS/LANL/CNES-IRAP/William Rapin
Using its laser technology, the Curiosity ChemCam instrument located the highest abundance of boron observed so far on this raised calcium sulfate vein. The red outline shows the location of the ChemCam target remote micro images (inset). The remote micro images show the location of each individual ChemCam laser point (red crosshairs) and the additional chemistry associated with each point (colored bars).  JPL-Caltech/MSSS/LANL/CNES-IRAP/William Rapin

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.”

The foreground of this scene from the Mastcam on NASA's Curiosity Mars rover shows purple-hued rocks near the rover's late-2016 location. The middle distance includes future destinations for the rover. Variations in color of the rocks hint at the diversity of their composition on lower Mount Sharp. Credits: NASA/JPL-Caltech/MSSS
The foreground of this scene from the Mastcam on NASA’s Curiosity Mars rover shows purplish rocks near the rover’s late-2016 location. The middle distance includes future destinations for the rover. Variations in color of the rocks hint at the diversity of their composition on lower Mount Sharp. NASA/JPL-Caltech/MSSS

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.

Steven Benner and his colleagues were the first to synthesize a gene, beginning the field of synthetic biology. He was instrumental in establishing the field of paleogenetics. He founded The Westheimer Institute of Science and Technology (TWIST) and the Foundation For Applied Molecular Evolution.
Steven Benner and his colleagues were the first to synthesize a gene, beginning the field of synthetic biology. He was instrumental in establishing the field of paleogenetics. He founded The Westheimer Institute of Science and Technology (TWIST) and the Foundation For Applied Molecular Evolution.

“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.

This pair of drawings depicts the same location at Gale Crater on at two points in time: now and billions of years ago. Water moving beneath the ground, as well as water above the surface in ancient rivers and lakes, provided favorable conditions for microbial life, if Mars has ever hosted life. Credits: NASA/JPL-Caltech
A drawing of Gale Crater as it is organized now.  Water moving beneath the ground, as well as water above the surface in ancient rivers and lakes, provided favorable conditions for microbial life, if Mars has ever hosted life. A well-done animation including a second drawing showing conditions 3.5 billion years ago at Gale can be seen here.   It toggles back and forth to show how things have changed.  (NASA/JPL-Caltech)

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.

The ChemCam instrument, with its laser zapper, identified the element boron as Curiosity climbs Mount Sharp. (NASA)
An illustration of the ChemCam instrument, with its laser zapper, which identified the element boron as Curiosity climbs Mount Sharp. (NASA)

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.

This view from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover shows an outcrop with finely layered rocks within the "Murray Buttes" region on lower Mount Sharp. (NASA/JPL-Caltech/MSSS)
This view from the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover shows an outcrop with finely layered rocks within the “Murray Buttes” region on lower Mount Sharp. (NASA/JPL-Caltech/MSSS)

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.






The Search for Organic Compounds On Mars Is Getting Results

This photograph, taken by NASA's Mars Rover Curiosity in 2015, shows sedimentary rocks of the Kimberley Formation in Gale Crater. The crater contains thick deposits of finely-laminated mudstone that represent fine-grained sediments deposited in a standing body of water that persisted for a long period of time - long enough to allow sediments to accumulate to significant thickness. Image by NASA. Enlarge image. [8]
Sedimentary rocks of the Kimberley Formation in Gale Crater, as photographed in 2015. The crater contains thick deposits of finely-laminated mudstone from fine-grained sediments deposited in a standing body of water that persisted for a long period of time.  Scientists have now reported several detections of organic compounds — the building blocks of life in Gale Crater samples. (NASA/JPL-Caltech/MSSS)

One of the primary goals of the Curiosity mission to Mars has been to search for and hopefully identify organic compounds — the carbon-based molecules that on Earth are the building blocks of life.

No previous mission had quite the instruments and capacity needed to detect the precious organics, nor did they have the knowledge about Martian chemistry that the Curiosity team had at launch.

Nonetheless, finding organics with Curiosity was no sure things.  Not only is the Martian surface bombarded with ultraviolet radiation that breaks molecules apart and destroys organics, but also a particular compound now known to be common in the soil will interfere with the essential oven-heating process used by NASA to detect organics.

So when Jennifer Eigenbrode, a biogeochemist and geologist at the Goddard Space Flight Center and a member of the Curiosity organics-searching team,  asked her colleagues gathered for Curiosity’s 2012 touch-down whether they thought organics would be found, the answer was not pretty.

“I did a quick survey across the the team and I was convinced that a majority in the room were very doubtful that we would ever detect organics on Mars, and certainly not in the top five centimeters or the surface.”

Yet at a recent National Academies of Sciences workshop on “Searching for Life Across Space and Time,” Eigenbrode gave this quite striking update:

“At this point, I can clearly say that I am convinced, and I hope you will be too, that organics are all over Mars, all over the surface, and probably through the rock record.  What does that mean? We’ll have to talk about it.”

 The hole drilled into this rock target, called "Cumberland," was made by NASA's Mars rover Curiosity on May 19, 2013. Credit: NASA/JPL-Caltech/MSSS
The hole drilled into this rock target, called “Cumberland,” was made by NASA’s Mars rover Curiosity on May 19, 2013.  One of the samples found to have organics was from the Cumberland hole. (NASA/JPL-Caltech/MSSS)

This is not, it should be said, the first time that a member of the Curiosity “Sample Analysis on Mars”  (SAM) team has reported the discovery of organic material.   The simple, but very important organic gas methane was detected in Gale Crater,  as were chlorinated hydrocarbons. Papers by Sushil Atreya of the University of Michigan and  Daniel Glavin and Caroline Freissinet from Goddard, along with other team members from the SAM team, have been published on all these finds.

But Eigenbrode’s work and her comments at the workshop– which acknowledged the essential work of SAM colleagues — move the organics story substantially further.

That’s because her detections involve larger organic compounds, or rather pieces of what were once larger organics.  What’s more, these organics were found only when the Mars samples were cooked at over over 800 degrees centigrade in the SAM oven, while the earlier ones came off as detectable gases at significantly lower temperatures.

Goddard biogeochemist Jennifer Eigenbrode, who is an expert at detecting organic compounds in rocks, is using R&D funds to develop a simplified sample-processing method that could be applied to a robotic chemistry lab. Photo Credit: Chris Gunn Summer 2008
Goddard biogeochemist Jennifer Eigenbrode, an expert at detecting organic compounds in rocks, has found them in Martian samples collected by the Curiosity rover.
(Chris Gunn)

These latest carbon-based organics were most likely bound up inside minerals, Eigenbrode said. Their discovery now is a function of having an oven on Mars that, for the first time, can get hot enough to break them apart.

The larger molecules bring with them additional importance because, as Eigenbrode explained it, 75 to 90 percent of organic compounds are of this more complex variety.  What’s more, she said that the levels at which the compounds are present, as well as where they were found, suggests a pretty radical conclusion:  that they are a global phenomenon, most likely found around the planet.

Her logic is that the overall geochemistry of soil at Gale Crater as read by Curiosity instruments is quite similar to the chemistry of samples tested by earlier rovers at two other sites on Mars, Gusev Crater and Meridiani Planum.

Many Mars scientists are comfortable with taking these parallel bulk chemistry readouts — the sum total of all the chemicals found in the samples — and inferring that much of the planet has a similar chemical makeup.

Taking the logic a step further, Eigenbrode proposed to the assembled scientists that the signatures of carbon-based organics are also a global phenomenon.

“I think it just might be,” she told the NAS workshop, which was organized by the Space Studies Board. “We’ll have to find out more, but I think there’s a good possibility.”

That’s quite a jump — from a situation not long ago when no organics had been knowingly  detected on Mars, to one where there’s a possibility they are everywhere.

The Sample Analysis on Mars instrument has the job of searching for, among other xxx, organics on Mars. And it seems to have succeeded, despite some major obstacles. (NASA/Goddard Space Flight Center)
The Sample Analysis on Mars (SAM) instrument has the job of searching for, among other targets, organics on Mars.  It heats the scooped or drilled samples to as much as 860 degrees C, cooking them until compounds come off in a gas form.  Then it sniffs the gases and identifies them.  It is the most complex instrument on Curiosity and has come up with important results, despite some major obstacles. (NASA/Goddard Space Flight Center)

And actually, they should be found everywhere.  Not only do organic molecules rain down from the sky embedded in asteroids and interstellar dust, but they can also be formed abiotically out of chemicals on Mars and, just possibly, can be the products of biological activity.

The fact that Mars surely has had organics on its surface and elsewhere has made the non-detection of organics a puzzle.  In fact, that conclusion of “no organics present” following the Viking landings in the mid 1970s set the Mars program back several decades.  If there weren’t even organic compounds to be found, the thinking went, then a search for actual living creatures was pointless.

As is now apparent, the Viking instrument used to detect organics didn’t have the necessary diagnostic power that SAM has. What’s more, the scientists working with it did not know about a particular chemical on the Martian surface that was skewing the results.  Plus the scientists may well have misunderstood their own findings.

First with the question of technological muscle.  The oven associated with the search for organics is part of a Gas Chromatograph Mass Spectrometer (GCMS), and it heats and breaks apart dirt and rock samples for analysis of their chemical makeup. The oven on the Viking landers only went up to 500 degrees C.  But the SAM oven on Curiosity goes hotter. It detected signs of organics between 500 and 850 degrees C.

In addition, NASA’s Phoenix lander discovered in 2008 that the Martian soil contained the salt perchlorate, which when burned in a GCMS oven can mask the presence of organics.  And finally, the Viking landers actually did detect organics in the form of simple chlorinated hydrocarbons.  They were determined at the time to be contamination from Earth, but the same compounds have been detected by Curiosity, suggesting that Viking might actually have found Martian, rather than Earthly, organics.

Image taken by Viking 2 on Mars in 1976. Results from both Viking landers reported no organic material in their samples, strongly suggesting there was no chance of current or past life. Recent readings by the SAM instrument on the Curiosity rover suggest the Viking conclusions were not correct, and that the instruments then did not have the capacity to detect Martian organics. NASA
Image taken by Viking 2 on Mars in 1976. Results from both Viking landers reported no organic material in their samples, strongly suggesting there was no chance of current or past life. Recent readings by the SAM instrument on the Curiosity rover suggest the Viking conclusions were not correct, and that the instruments then did not have the capacity to detect Martian organics. (NASA)

What makes carbon-based organic compounds especially interesting to scientists is that life is made of them and produces them.  So one source of the organics in Martian samples could be biology, Eigenbrode said.  But she said there were other potential sources that might be more plausible.

Organics, for instance, can be formed through non-biological geothermal and hydrothermal processes on Earth, and presumably on Mars too.  In addition, both meteorites and interstellar dust are known to contain organic compounds, and they rain down on Mars as they do on Earth.

Eigenbrode said the organics being detected could be coming from any one source, or from all of them.

Asked at the workshop what concentrations of organics were found, she replied with a grin that more light will be shed on the question at next week’s American Geophysical Union meeting.

The detection of a growing variety of organics on Mars adds to the conclusion already reached by the Curiosity team — that Mars was once much wetter, warmer and by traditional definitions “habitable.”  That doesn’t mean that life ever existed there, but rather that what are considered basic basic conditions for life were present for many millions of years.

Eigenbrode said that the detection of these carbon-based compounds is important in terms of both the distant past and the perhaps mid-term future.

For the past, it means that organics in a substantial reservoir of water like the one at Gale Crater some 3.6 billion years ago could have been a ready source of energy for microbial life.  The microbes would then have been heterotrophs, which get their nutrition from organic material.    Autotrophs, simpler organisms, are  capable of synthesizing their own food from inorganic substances using light or chemical energy.

But Eigenbrode also sees the organics as potentially good news for the future — for possibly still living microbes on Mars and also for humans who might be trying to survive there one day.

“Thinking forward, the organic matter could be really important for farming — a ready energy source provided by the carbon,”  she said.

Just what a human colony on Mars some day might need.