Yesterday, the journal Science published several provocative reports about new geological findings on Mars. These findings come from the Mars Science Laboratory, that the world called “the Curiosity rover.” In swift sequence, the world heard of methane and methane-like compounds on Mars, and then of water on Mars – a lot of it. This excited anew the debate on whether Mars harbors life, or was an origin of life. At least one scientist, after reading the reports, makes a remarkable suggestion: yes, Mars might harbor life. If it does, that life did not spring forth from Mars. Instead, that life, and the water, might have come from earth – and not as recent contaminants, either.
The Curiosity rover and why it is so important
The Curiosity rover landed on Mars on August 6, 2012. That in itself excited the world, as it should have. The Mars Science Laboratory (the formal name of the Curiosity rover) is the heaviest, most sophisticated, and the most delicate instrument ever to land on Mars. It carries several different types of camera, plus a compact sample analyzer that can measure very small amounts of whatever makes up a sample. The landing needed many different steps. If one step had failed, the Curiosity rover would be a useless pile of junk. But it landed safely. So it gives humanity the best chance to study Mars short of landing a crew on it. (And that kind of project would be far too expensive to lay on only to do geology, or “areology,” on Mars.)
The National Aeronautics and Space Administration (NASA) built and launched the Curiosity rover to help settle, if anyone can, whether Mars has life on it. Scientists have wondered about life on Mars at least since Percival Lovell first looked at Mars through a telescope and described what looked like “channels” on its surface. Lurid visions of an advanced, and even hostile, civilization pleasantly titillated laypeople for decades. Then the first Mariner rocket probes went into orbit around Mars, looked down, didn’t get shot down, and found no sign of civilization, friendly or unfriendly. So scientists decided Mars might have lichens growing on its surface. Thus far, no one has found even that.
The Viking landers found chloromethanes (methyl chloride, methylene chloride) in 1976. But one team decided someone, after cleaning the instruments to pack them for launch, didn’t rinse them properly. (See this article in yesterday’s issue of Science, by Leshin et al., for that detail.) We may assume whoever packed the Curiosity rover for launch did not make that same mistake.
The latest findings from the Curiosity rover
Yesterday, Science published a special issue full of articles on findings by the Curiosity rover. John P. Grotzinger introduced it and summed up the five articles in the special issue:
- Stolper et al, “The Petrochemistry of Jake_M: A Martian Mugearite” <http://dx.doi.org/10.1126/science.1239463>
- Meslin et al., “Soil Diversity and Hydration as Observed by ChemCam at Gale Crater, Mars.” <http://dx.doi.org/10.1126/science.1238670>
- Bish et al., “X-ray Diffraction Results from Mars Science Laboratory: Mineralogy at Rocknest at Gale Crater.” <http://dx.doi.org/10.1126/science.1238932>
- Blake et al., “Curiosity at Gale Crater, Mars: Characterization and Analysis of the Rocknest Sand Shadow.” <http://dx.doi.org/10.1126/science.1239505>
- Leshin et al., “Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover.” <http://dx.doi.org/10.1126/science.1238937>
To read these articles in full, one must subscribe to Science.
The Jake_M rock itself is remarkable. Grotzinger describes it as “a loose rock sitting on the plains.” It stands out because it looks like an Earth rock! To be more specific, it looks and tests like a rock one might find on an island in the Pacific Ocean, or at a continental rift. Stolper, in his article, makes the point more forcefully: now that the Curiosity rover found one such rock, it might find more. Many more.
Jake_M wasn’t exciting enough for the lay press to talk about it. But the findings by Leshin and her team were. The other three articles put those findings into perspective. One needs to consider all of them together to recognize what they imply.
The finding everyone’s talking about is the water. The Curiosity rover sampled windblown sands from a “sand shadow” called Rocknest. The Leshin team found water bound to these sands, varying from about 1.5 to 3 percent by weight. From earlier reports, Leshin infers that this ratio holds all over Mars, not in only one place.
But that’s not all. The Bish and Blake papers show that from a quarter to half those sands are amorphous material. And the water came from those amorphous sands.
Why does this matter? In an exclusive interview, Walter T. Brown pointed out that amorphous sands are more likely to have formed in space, while crystals form where gravity is reasonably strong. If the water comes from the amorphous sands, the water likely came from space.
The Leshin paper gives more evidence, from isotope analysis. Leshin reports that:
Hydrogen in all Rocknest samples is highly enriched in deuterium compared to terrestrial materials.
Deuterium, or heavy hydrogen, weighs twice as much per atom as regular hydrogen. Deuterium forms when a flood of neutrons tries to go through a large body of water. The water, or at least the hydrogen, captures the neutrons. Deuterium has one proton and one neutron; regular hydrogen does not have the neutron.
The Rocknest sample had eight times the strength of deuterium, for the amount of regular hydrogen, that one finds in the earth’s oceans. Then again: the earth’s oceans are richer in deuterium than is the rest of the solar system, though comets are also richer in deuterium than our oceans. Where did this heavy hydrogen come from?
Finally: the Curiosity rover found four different chlorinated compounds: methyl chloride, methylene chloride, chloroform, and chloromethylpropylene. Recall that Viking found the first two, but scientists then thought the cleaning solvents They can’t lay the blame there now. The Curiosity rover found far more of these compounds this time. More than that, the controllers ran an internal control and found no such compounds in that test.
What these findings mean
The chlorohydrocarbons are a puzzle. The Leshin team can’t settle on where they come from. The Curiosity rover’s instruments also find oxygen and hydrochloride in the same reaction. So the Leshin team speculates that an “oxychloride compound” is reacting with another source of carbon: either from the instruments, or a falling meteoroid, or from Mars itself.
But methyl chloride (monochloromethane) comes naturally from plankton or the salt marsh. Chloroform comes from many seaweeds, algae, and other marine plants. No one has yet found anything like that on Mars. But perhaps extremophiles exist that produce these compounds, and the other two chlorohydrocarbons the Curiosity rover found. If Mars harbors any life forms at all, they would most likely be extremophiles – micro-organisms that live in environments where nothing else can live.
The water findings suggest something so provocative that no one wants to talk about it. Two pieces of evidence stand out. First is that the water comes from amorphous solids, solids that likely formed in space. Second is the deuterium. For according to Brown, one event, about five thousand years ago, produced a large flow, or “flux,” of neutrons through water that likely produced all that deuterium. That event was the Global Flood.
Dr. Brown explains it this way, beginning here: the “fountains of the great deep” were from a subcrustal ocean. This ocean broke out from a rupture in the earth’s crust. (Today the Mid-Oceanic Ridge marks the path of that rupture.) The tremendous jet of water rushing out through the seam made its edges flutter. And on that scale, that “flutter” produced magnitude-10-to-12 earthquakes. Those earthquakes deformed the abundant quartz in the crust, and produced enough electromotive force to make super-heavy elements. Those elements then split to form the trans-lead elements we know today, from bismuth to uranium and maybe to neptunium and plutonium, too.
All those nuclear reactions released the greatest flux of neutrons the world has ever known. Most of these neutrons flowed into the subcrustal ocean water. This water absorbed the neutrons and changed from the normal H2O to HDO – hydrogen deuterium oxide, or heavy water. (Scientists know of an even rarer and heavier water, D2O.)
An amount of water, rock and mud, together weighing about 5% as much as the moon, shot away from earth in all directions. (The earth never stopped spinning.) The comets hold much of this water. This water also has twice the deuterium one finds in earth’s oceans. Any deuterium-rich water on Mars most likely comes from the same source: either comets that fell to Mars, or some of the same water that came together and froze to make the comets.
If any of this water, with the high proportion of heavy water, held those hardy forms of life we call extremophiles, that could explain the chlorohydrocarbons. Viking first found them, and now the Curiosity rover has found even more of them.