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Life on Mars:

March 22, 2002.

Martian dark spots under debate - Physical or biological?

In the beginning of last year, "wild claims" appeared on several web sites considered as "dubious" or of the "lunatic fringe" kind. The "claims" were that the Mars Global Surveyor orbiter camera photographs of Mars show "vegetation" and "artificial glass tubes."

It did not take me long to check it out. The photographs were authentic and unaltered, often with references to the original and official Mars Global Surveyor photograph publishing server at the Malin Space Science Center.

There were two kinds of images involved:

First, the images showing alleged "artificial glass tubes" did only show sand dunes stretched at the bottom of canyons. The wind created these. They were not of glass, and not artificial. I could not even understand how the idea came out, because you only had to look at nearby pictures to see that fields of dunes has exactly that aspect, and the "tubular" aspect was obvious: the "tubes" were in canyons. Case closed for me!

The second type of images were much more interesting. They did show something resembling bushes or even trees, sometimes with shadows. These "bushes" or "trees" or "giant fungi" do indeed look much like vegetation. But JPL had an other explanation: they were traces of defrosting, when the ice, water ice or carbon dioxide ice, in the permafrost heated in summer, it did not melt as a liquid but immediately and violently vaporized as a gas, because of the harsh conditions of Mars not allowing liquid water. I had already challenged the notion of the impossibility of liquid water, and many scientists agreed that liquid water on Mars is sometimes possible, but near the south pole where the "bushes" were shown, the JPL explanation made sense.

JPL stated it in the pictures captions: "attention, it looks like bushes but it is not bushes!" and in the page I devoted to these new images, I quite agreed that it seemed a good explanation, unless new data challenge it in the future. Why shout "vegetation!" if there is a more trivial and economical explanation? I was already convinced by the results of the Viking experiments combined with our better knowledge of Mars that there is life on Mars, very probably in the form of small microbes, but the "bushes" did not convince me and the "glass tubes" fantaisies pointed out that things seen from space on another planet are not necessarily to be taken for granted.

Then, the wide audience vulgarization web site run a story according to which the famous Science Fiction writer Arthur C. Clarke of "2001" fame stated in a interview that these "bushes" are indeed the proof that there is vegetation on Mars. Unfortunately, the interview was removed from the web site. How did I know? Well, not only because people said it was there, but because their site search still had the reference to the missing page, including the first lines. Search indexes are not necessarily updated every time a page is deleted of course, but I found this rather funny. Because Sir Clarke also mentioned the infamous "glass pipes," I thought that Science Fiction writers are definitely not scientists and have fantaisies of their own. If Sir Clarke had looked at the JPL comment of the "bushes" images, maybe he would have agreed with their explanation.

But then again, and other similar sites,, and other announced that "a team of Hungarian scientists has discovered the proof that there is vegetation on Mars in the MGS images." The Hungarian team has examined the southern spots in detail and reported that the spots appear in late winter and then disappear by summer. I wondered if they forgot to read the JPL explanation, or if they had found new reason to challenge it, but none of the news items was in-depth enough to find out. So the "bushes" were still defrosting traces to me, and their seasonal changes are not at odds at all with this trivial interpretation.

Enter now the European Space Agency scientists. They wonder if the Hungarian team may be right.

If they think so, they will have a look with ESA's planned Mars Express, scheduled to orbit the planet beginning in late 2003.

Luckily, new work has now indicated why scientists did not agree with the physical explanation and favor the biological explanation instead: the spots appear first at the margins of the dune fields but rarely on the dune ridges. Their location (which is independent of the elevation of the land) and shape (which is circular on flat surfaces but elongated on slopes) seems to be at odds with a physical explanation alone.

Better information about the "hungarian scientist" is now available: András Horváth, Tibor Gánti and Eörs Szathmáry from the Planetarium and the Institute for Advanced Study, Budapest, suggested the spots could be colonies of Martian microbes which wax and wane with the season. They hypothesize the spots are colonies of photosynthetic Martian microorganisms, which over-winter beneath the ice cap. As the Sun returns to the pole during early spring, light penetrates the ice, the microorganisms photosynthesize and heat their immediate surroundings.

A pocket of water, which would normally evaporate instantly in the thin Martian atmosphere, is trapped around them by the overlying ice. As this ice layer thins, the microorganisms show through in the color gray. When it has completely melted, they rapidly desiccate and turn black. This explains why many dark dune spots have a black center surrounded by a gray aureole, the Hungarian scientists said.

The subject is now under heavy debate. It led to a meeting at ESA's ESTEC technical center in the Netherlands. Agustin Chicarro, ESA project scientist for Mars Express, initiator of the meeting, stated: "As a geologist, I found the spots quite perplexing and very exciting. I wanted to tap a broad spectrum of expert opinion to decide whether they warrant closer examination by Mars Express."

"Images taken by the Giotto spacecraft showed that the black color of cometary nuclei is formed when a mixture of carbon and water ice is exposed to ultraviolet radiation," he said. Experiments on board Mars Express could help to determine whether the same had happened on Mars.

One part of the debate makes no great sense of course: skeptics of the biological hypothesis still refer to the "extreme harsh conditions" on Mars to consider that life is "impossible" on Mars or find the idea "hard to believe". The truth is, nobody knows just how tolerant life can be to these and other environmental stresses, and nobody can be certain that some particular geological process such as gas releases could not be a factor helping biological activity. Just as gas release could be responsible for the spots without biological activity, they may also fuel biological activity.

Also true and known to the readers of my site, the conclusion that "Viking did not find biological activity" is a conclusion I oppose. I have read the papers by Gilbert Levin and other and as time goes by, his arguments gets stronger and stronger. They convinced me - and other - that there is at least some microbial life on Mars, probably hibernating - but we now know that bacteria can hibernate for at least million years and even survive inside space rocks.

As indicated in my news section, the Mars Odyssey probe already detected evidence of large quantities of water on Mars, while the instruments were not even performing productive measurements but merely tests. Then, we learned stunning "meteorological" news claiming that Mars "is terraforming," "Mars' climate will be suitable for human presence in a few centuries if the climate continues its current change rate," and so on.

What I would now like to get from the scientists is the following:

How salty must water be for NOT to freeze at which temperature below zero? And what are the results when the air pressure density is added? What is the conceivable limit for some imaginary protein to force cold water to stay liquid?

What is the real temperature on Mars? I have located several temperature charts of the planet temperature seemingly indicating large equatorial zones above 0 degrees Celsius. Air or ground temperature? Is the ground warmer or colder than the air, and where? And most of all, when? Mars' orbit is not circular but slightly elliptical, the planet moves closer to the sun at periods. What is the effect of that on the temperature conditions and on the density of the atmosphere, particularly with a powerful greenhouse effect created by the release of large amounts of carbon dioxide?

When I was a young boy, my grandfather showed me some souvenirs about his stay in the Saharian desert while he was in the military. One interesting piece was a very strange piece of vegetation. It was a five inch diameter plant, totally desiccated, it had to be handled with care because otherwise it would break in pieces. But if you placed this plant on a saucer with 1 or 2 millimeter of water, the plant grew to triple its size in literally a few minutes. It rescucitated. Put it out of the saucer, and in just a few minute, it went back to its completely desiccated state. It "looked dead" again, and my grandfather could put it back in the shoebox where it was stored for more than 40 years. How far fetch is it to imagine similar but much, much more powerful capacities of some Martian vegetation or fungi?

You will find many more arguments in the Mars section of my website.

"We have to go there," say some scientists. The voice of reason.

Of course, some have already prepared the argument that if life is detected, we will have to prove that it is not due to a contamination imported on Mars by the future lander. But if life manifests itself there as "large scale" vegetation, we would get a different story.

Several papers on dark dune spots on Mars are scheduled to be presented at the European Geophysical Society annual conference in Nice, France, April 22-26.

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This page was last updated on March 22, 2002.