Many scientists think that the Ancient Martian Ocean Would Have Been Salty ‘Dead Sea’.
ByANDY FLEMING
Evidence is mounting that Mars was once a wet and warm world, similar to the early Earth. What went wrong with the Red Planet -- is it possible that future explorers may find fossils from a more habitable time -- indeed did microbial life survive until the present time?
Once upon a time there were two adjacent planets orbiting a run-of the-mill star in one of the arms of an unremarkable spiral galaxy. Both were warm, both were wet, both had substantial atmospheres, both had vulcanism, both had oceans, seas and rivers, and both were in or on the edge of their star’s habitable zone. Life, we are certain began on one, but on the other – well we’re not too sure.
The planets in question are of course the Earth and Mars. Everyone is fascinated by Mars. From an earlier less-informed age, science fiction by Ray Bradbury and Edgar Rice Burroughs, or the imagined canals of astronomer Percival Lowell has fired our imagination, and has ensured that the Red Planet now has a special place in both our hearts and popular folklore.
The real Mars is even more fascinating however, and the planet’s formation and history can be the subject of some fascinating speculation. Mars is still one of the few places in the solar system that humans can think realistically about exploring on foot. Did life arise on Mars in its early past like it did on Earth? Even more speculatively, did life arise on one planet, only to be transported by ejecta to the other after an asteroid impact? Many scientists think that life, well microbial life at any rate, protected from cosmic rays and a fiery entry into the Earth’s atmosphere inside a space rock can traverse the vast distances between planets.
One of the meteorites discovered on the snows of the Allen Hills of Antarctica showcased by NASA in 1996, and confirmed as Martian by isotopic analysis, contains tantalising crystal structures that may be either chemical in origin or fossilised bacteria (albeit very small bacteria!). Meteorite ALH84001 may surprise us yet. Will future geologists as they explore Mars discover fossils in the sedimentary rocks that are so indicative of the planet’s wet and warmer past? Did creatures swim in the seas and rivers of ancient Mars – were they washed up on the now high and dry fossilised Martian beaches that we’ve identified with our Mars orbiters? Did they take the ultimate white-knuckle ride over waterfalls to dwarf Niagara in the Vallis Marineris, a gargantuan canyon the length of North America? As the late NASA astronomer and planetary scientist Carl Sagan (1994) speculated, “Now that would be a world to explore – unfortunately we are four billion years too late!
Whether such speculation turns out to be confirmed, things started to go wrong with Mars about 3.8 billion years ago, about the time life got started on Earth. Mars is about half the size of the Earth so its interior began to radiate heat to space much more quickly and its core began to solidify. Without a molten iron core acting as a dynamo, any magnetic field surrounding the planet started to dissipate exposing the atmosphere and surface to the Sun’s charged particles. Any tentative carbon cycle would grind to a halt too -- despite having the largest volcano in the solar system (Olympus Mons), vulcanism would cease, and with it any possibility of recycling the planet’s carboniferous rocks.
