Life on Mars constrained further!

[GrandMasterTerwynn]

Planet was wet only for first 600 million years.

Study Reveals Young Mars Was A Wet World
By Ker Than
Staff Writer
posted: 20 April 2006
02:00 pm ET

The most comprehensive study ever conducted of minerals on Mars' surface reveals the planet has undergone three distinct geological eras throughout its history, with water playing a progressively lesser role in each.
If life as we know it here on Earth ever existed on the red planet, it could only have survived in the planet's infancy, during the earliest era, the study concludes.
"Starting about 3.5 billion years ago, conditions on Mars became increasingly dry and acidic—not a pleasant place for any form of life, even a microbe," said study team member John Mustard, a geologist from Brown University.
The mineral maps were created using data from OMEGA, the major spectrometer aboard the Mars Express, as well as related observations collected by other Mars orbiters and the two rovers.
The study, led by Jean-Pierre Bibring from the University of Paris, is detailed in the March 21 issue of the journal Science.
The three faces of Mars

Based on their analyses, the team divided Mars' geological history into three distinct eras:

The first era, which lasted from about 4.6 billion years ago to 4 billion years ago, was a relatively wet one. The oldest rock—exposed by erosion, impact or faulting—showed the presence of clay minerals, such as chamosite and nontronite, that require abundant water, moderate temperatures and low acidity to form.

The next era was drastically different. Massive volcanic eruptions spewed sulfur into the atmosphere, turning the planet's moist and alkaline environment to a dry, acidic one. This period lasted form about 4 and 3.5 billion years and is evidenced by minerals such as gypsum and grey hematite, which were found in Meridiani and in Valles Marineris.

Minerals from the most recent era, which began about 3.5 billion years ago and continues to the present, show no evidence of forming with, or being altered by, liquid water. These iron-rich minerals, mostly ferric oxides, were found across most of the planet and reflect the cold, dry conditions that persist on Mars to this day.

The new study also revealed what is responsible for Mar's reddish hue: most likely, the researchers say, the red planet gets its color from tiny grains of red hematite or possibly maghemite, two minerals that are riddled with iron.

A target for future mission

If Martian life ever did exist, it could probably have only survived during the first era, the team reports. And evidence for that life is most likely to be found in the Syrtis Major volcanic plateau, in Nili Fossae and in the Marwth Vallis Regions, two regions rich in the clay minerals abundant during Mars' youth. The researchers added that these areas would make compelling targets for future lander missions.

The basic summary of this is that Mars has been cold and dead for the last 3.5 billion years, and was only wet and habitable for the first 600 million years of its history. It became inhospitable pretty quickly, in geologic terms. On one hand, it gives us good places to look for fossilized remains (in the absolute oldest Martian rocks) and what to look for (primitive microbes.) On the other hand, it tells us that life wasn't likely widespread on Mars, and that finding it today would be a pretty long stretch.

[Lord Zentei]

Unfortunately, if we're talking about Pre-Cambrian level lifeforms (which seems likely given the timeframe that they had for evolution) we won't find very much of anything as far as fossils are concerned.

[GrandMasterTerwynn]

Unfortunately, if we're talking about Pre-Cambrian level lifeforms (which seems likely given the timeframe that they had for evolution) we won't find very much of anything as far as fossils are concerned.

Yes, about all we can hope for are gas bubbles trapped in zircon crystals, or microfossils embedded in four billion year old clay. The planet probably wasn't wet enough, nor was the life developed enough for us to find anything that we could definitely call the artifacts of life, such as stromatolites.

[Junghalli]

Well, if life did evolve it just might survive in some form. Life is pretty hardy and damned hard to completely kill off once established. Question is would six hundred mya have been enough?

[Lord Zentei]

Well, if life did evolve it just might survive in some form. Life is pretty hardy and damned hard to completely kill off once established. Question is would six hundred mya have been enough?

I don't think so. The Hadean stretched from 4500 mya to 3800 mya, which is about 700 million years, and it was after this - during the Archaean - that life first appeared, as far as I'm aware.

[Nieztchean Uber-Amoeba]

So the only surviving creatures will be Oscar Wilde.

[Ariphaos]

Well, if life did evolve it just might survive in some form. Life is pretty hardy and damned hard to completely kill off once established. Question is would six hundred mya have been enough?

It's becoming increasingly apparrant that life on Earth began quite early. I would imagine that some clays will contain such microfossil imprints, and that would be extremely cool, but four billion years of an extremely hostile environment is going to significantly tax any lifeform.

[Drooling Iguana]

At least that means that we won't have to worry about wiping out an existing ecosystem when we start terraforming the place.

[Alyeska]

From the evidence I have seen, I would give it a 50/50 chance that some form of life did evolve on Mars in its early days. It didn't take life very long to form on Earth and we have found some very old remnants of it.

Now, while Mars has been cold and dead for a very long time, there is evidence of recent water activity on the planet. This can be from the shifting poles which would take previously frozen water altitudes and move it into warmer climate which could cause temporary melts in the water. There is a slight chance that some life has somehow survived on Mars. Life on Earth can be a tenascious thing which can live in inhospitable enviroments. I could see some microbes potentialy surviving. I won't lay odds on that, but I wouldn't be surprised if some where found in the next centuries.