Mars needs 'magic triangle'
2005-08-14 15:28
Paris - Scientists will be thrilled by any data the new US mission to Mars gets that points to abundant water on Mars even if, at present, we only know it to be ice rather than liquid and located at the poles.
Water is one side of a "magic triangle" that comprises the main ingredients for making life or, more exactly, life as we conceive of it.
The three sides of the triangle
After Earth, Mars is the only other planet of the solar system where there is a reasonably good chance of all the ingredients coming together.
If something like bacteria - even fossilised - is found on Mars, it implies we are not alone.
David McKay, an expert at Nasa's Johnson Space Centre, has said there is already evidence of primitive bacterial life on Mars. He said it was in a meteorite found in Antarctica and believed to be from Mars.
Water
Water nurtures life forms and enables them to evolve. The oceans that cover two thirds of the Earth's surface are believed to have been the cradle of life on this planet.
Liquid water, rather than ice, is essential because it is the right temperature at which many elements dissolve in it and react. This does not happen with ice.
There is evidence of ice on the surface at the Martian poles.
According to David Shuster of the California Institute of Technology and Benjamin Weiss of the Massachusetts Institute of Technology, there has been no significant amounts of water on Mars for more than four billion years.
Energy
As for energy, Mars is well favoured in sunlight, the source that powers photosynthesis and thus, indirectly, all life on Earth.
Being the fourth planet, farther from the Sun than Earth, Mars is far colder and darker than Earth.
But compared with the outer planets, it is warm and light. At summer on the Martian equator, the temperature reaches 27 degrees Celsius.
And the planet turns quickly on its axis - a Martian day is only slightly longer than an Earth day.
This means that light and heat are distributed swiftly and evenly.
That contrasts with planets where a "day" can last months in equivalent Earth terms, plunging half of the surface in prolonged frigidity.
Chemical building blocks
Of the chemical building blocks, carbon, hydrogen, oxygen and nitrogen are the big ones because they can combine in thousands of ways to form compounds.
Water will provide hydrogen and oxygen, carbon's two elements.
The first mineral-tasting tests carried out by the US robotic explorer Spirit last week showed an abundance of olivine, a mineral with silicon, oxygen, iron and magnesium.
And the planet's ruddy surface is widely attributed to iron in rocks that, over billions of years, dissolved into the planet's surface water, oxidised and was then deposited by winds across the surface after the waters mysteriously disappeared. But a caveat must be added.
If all three sides of the "magic triangle" existed on Mars, there is still no proof of life.