Aliens, Are we alone in this Universe? Options

[vivekpm]

Aliens!!! This is the topic which intrigues me everytime I ponder upon it...

I used to run SETI sometime back hoping that I would some day help in making contacts with extra-terrestial creatures .

Would like to invite talks on this topic. One thing that I have always wondered is why have most, if not all, research on aliens concentrated in finding possible places in universe which can support life, that is, which has water in some form, sustainable temperatures etc...? Is it not possible that the definition of life can be different for aliens? I mean they may not require water at all. They may sustain only at 1000+ temperatures or at sub-zero temperatures. Why is this not possible? After all, the notion that to sustain life we need favourable conditions like presence of water etc., is concieved by us. For aliens, "favourable conditions" may be different.

Would request anyone who has done some reading on this to please throw more lights and possibly supply pointers to good research material...

Cheers,
Vivek...

PS: Thanks NimmiJi for this new forum...

[vivekpm]

Soil minerals point to planet-wide ocean on Mars

An ocean of water once wrapped around Mars, suggests the discovery of soil chemicals by NASA’s rovers. But the same chemicals also indicate that life was not widespread on the planet at the time the ocean was present.

Sulphates, which form most readily in liquid water, had already been detected by the Spirit and Opportunity rovers. The minerals have been interpreted as evidence for past bodies of water on the surface. But it has not been clear how large these bodies of water might have been.

Now, a new analysis of rover data suggests that the sulphates were once dissolved in a planet-wide ocean. The study was carried out by James Greenwood of Wesleyan University and Ruth Blake of Yale University, both in Connecticut, US.

The researchers point out that phosphates, which are also linked to water, are also present at both sites. More importantly, the ratio of phosphates to sulphates is about the same at both locations. They say the most likely explanation for this is that any local variations were smoothed out by mixing in a planet-wide ocean.


Acidic sea
Some researchers argue that a broad, flat area in Mars's northern hemisphere is the relic of an ancient ocean, and point to rock weathering that could have been caused by seawater. But the uniform phosphorus-to-sulphur ratio is the first chemical evidence that such a large body of water might have once existed.

The phosphorus was probably leached from rocks in the form of calcium phosphate, the researchers say. The fact that it appears to have been dissolved and mixed with sulphates in large amounts suggests that the hypothesised ocean must have been very acidic, because calcium phosphate only dissolves well in acidic water.

A phosphorus-rich ocean is a bad sign for past Mars life. Phosphorus is an important element for life on Earth, and is quickly extracted from the environment by organisms. If life were extensive on Mars, it would not have left so much phosphorus dissolved in the water, the researchers say.

"To a first order approximation, you couldn't have had a biosphere that was anything like the one on Earth," Greenwood says.


Lots of lakes?
Michael Wyatt of Brown University in Rhode Island, US, says the idea of a past ocean on Mars fits well with the phosphorus and sulphur data, but adds that several smaller bodies of water might also explain it.

"It's kind of hard to pin down smaller bodies of water versus one large ocean," he told New Scientist. Another possible explanation for the data would be many bodies of water that have similar chemistry, he says.

The researchers admit that the similar phosphate-to-sulphate ratio seen on opposite sides of the planet could also arise if wind mixed these materials together after the bodies of water disappeared.




Journal reference: Geology (vol 34, p 953)

Source

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