A Franco-American research team demonstrates the possibility of the presence on the red planet of a large marine expanse, there are three billion years ago.
by
Although some media and research organizations do, at regular intervals, seeming to discover it to stir up the curiosity of the public, the case has long been heard: water sank in Abondence. It has printed its mark in the geology where the experts see valleys dug by rivers, deltas or traces of old lakes. Remained to know if the red planet, now cold and dry, had been able to welcome a whole ocean. Posted on Tuesday 18 January by Proceedings of the National Academy of Sciences (PNAS) , modeling by a Franco-American team responds in the affirmative.
The scientific dispute around this question is not new, indicates the first author of this article, Frédéric Schmidt, Professor at Paris-Saclay University: “The controversy started in the 1980s, when we discovered River lines, and it is still vivid. “One of the major arguments against the ocean thesis consisted that a great sea could remain in time. Located far from the sun – which distributed less energy in its youth – the planet Mars did not perceive, 3 billion years ago, that 30% of the solar flow received by the Earth today and it had to do it already cold. If cold a possible ocean would not have survived: which would not froze itself would have evaporated and would have been transferred in the form of snow on the highlands of the South Martian hemisphere.
The challenge of researchers was therefore to find a mechanism for keeping the temperature of the former March and its paleo-ocean at a decent level, located all around the North Pole. “For that, explains Frédéric Schmidt, you have to start with a fairly obvious thing, add co 2 to inflate and warm the atmosphere. But that’s not enough. You must also inject 10% injecting 10%. of dihydrogen, which is a much more powerful greenhouse gas. It can thus obtain sufficiently mild temperatures to have liquid water on Mars. “
Hot currents to the pole
But that’s not all. Fill an ocean, it’s good; Prevent it from freezing and managing itself to keep it full, with a cycle of water, it’s better. The authors of the PNA study modeled the ocean circulation to realize that “it brought hot currents of the average latitudes to the pole,” says Frédéric Schmidt. This thermal machine is surprisingly effective, which maintains water between 1 and 4.5 ° C even if the average temperature on Mars is less than 0 ° C. The researchers have also shown that the great glaciers of the highlands flowed towards the ocean and brought it something to compensate for evaporation.
You have 33.5% of this article to be read. The rest is reserved for subscribers.