The climate of Mars at the very beginning of its history is the subject of fierce controversy. Was the Red Planet warm and humid or cold and snowy? A new study published in Icarus supports the latter. Today we know that Mars is dotted with networks of valleys, deltas and lacustrine sediments, which means that one day water must have flowed on the surface - about 4 billion years ago. Until now, climatologists have failed to create a climate model warm enough to make water on the surface of Mars liquid.
“People are trying to model the ancient climate of Mars using the same models that we use on Earth, and they are not quite successful. It is difficult to create warm ancient Mars because the sun was much weaker back then. The entire solar system was colder,”says Briony Horgan, assistant professor in the Department of Earth Sciences, Atmospheric and Planetary Sciences at Purdue University. "And while humans use climate models, we come from our point of view - what do the volcanic records tell us about Mars?"
There was a lot of volcanism throughout the early history of Mars. There are large volcanoes in some of the well-studied areas of the planet, but little is known about regions of low and smooth topography in this regard. There are about 100 flat hills on Mars, known as the Sisyphus Hills, which can be volcanic in origin.
When volcanoes erupt beneath ice sheets and glaciers on Earth, the combination of heat and melt water creates flat, steep, flat-topped mountains known as tuya. When subglacial eruptions do not disturb the ice surfaces, the tops of the volcanoes remain conical rather than flat. The mineralogy produced during these events is made unique by the effects of hot lava and cold glacial melt water.
Scientists used images from CRISM spectrometers to determine if the mineral composition of the region corresponded to sub-ice volcanism.
CRISM captures both visible light waves and shorter wavelengths to help instrument operators identify a wide range of minerals on the surface of Mars. The visible wavelengths are strongly influenced by iron, while at infrared wavelengths, CRISM catches the signatures of carbonates, sulfates, hydroxyl groups, and water incorporated into mineral crystals.
“Each breed has its own specific imprint, and it can be identified by the reflections of light,” says Sheridan Akiss, author of the work. Scientists have identified three specific combinations of minerals in the region, dominated by gypsum, polyhydrate sulfates, and a mixture of smectite-zeolite-iron oxide - all associated with volcanoes in glacial environments. “We now have all the minerals and morphology data that say there must have been ice on Mars at some point in time. And it was probably relatively late in the history of young Mars."
Ilya Khel
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