Mars used to have wet and dry seasons similar to ones on Earth

Ancient Mars had seasonal climate just like Earth’s, with alternating moist and dry seasons, in accordance with mud patterns found by NASA’s Curiosity rover. These seasonal cycles could have helped kind a few of the extra advanced constructing blocks for all times, resembling RNA and primary proteins.

There is ample proof that Mars as soon as had liquid water within the type of lakes and rivers, but it surely was unclear whether or not these got here from one-off occasions, resembling meteor impacts or volcanic eruptions melting ice, or whether or not they have been tied to a extra world climate cycle.

Now, William Rapin on the University of Toulouse, France, and his colleagues have examined pictures from Curiosity and located a particular sample of hexagonal ridges in mud from the Gale crater, a former lake, which they are saying can solely be shaped from repeated moist and dry environments, every lasting round a Martian 12 months or much less.

“It’s the first time we can show that the climate sustained hydrological change seasonally, or wet and dry seasons,” says Rapin. “We knew the Earth had them, but we didn’t know of any other planets that did. Now we know Mars had seasons.”

The researchers assume the ridges have been initially cracks in mud which have dried out. The cracks, which are inclined to intersect at particular angles, would have been stuffed in by flooding and minerals. Some of this materials would have been washed away, however a extra resilient mixture of mud and rock would have remained, forming the ridges. “Only a seasonal climate – something with high frequency, geologically speaking – can produce those cracks in the mud that got fossilised,” says Rapin.

The hexagons are all about 4 centimetres large, which Rapin and his colleagues used to estimate that the water depth was about 2 centimetres. This means that these cycles have been pretty common, lasting round a Martian 12 months on the time, and will have continued for hundreds of thousands of years.

Some environments on Earth show related patterns, resembling in California’s Racetrack Playa, which is a dry lake for many of the 12 months however fills with a shallow layer of water within the wet season.

These rock formations seem like about 3.6 billion years outdated. This is across the time we all know that life first emerged on Earth, which suggests there ought to have been sufficient time for all times to have emerged on Mars, too. “If you have life on Earth, then why not life on Mars, if conditions on both planets were about the same,” says Mark Sephton at Imperial College London.

The seasonal climate might even have helped kind molecules important for all times, like RNA and proteins, from small constructing blocks of natural matter, resembling amino acids and nucleotides. Lab experiments have proven that the chemical reactions required, like polymerisation and condensation reactions, typically want intervals of dehydration.

“If you’ve got a primordial soup, and you dry things out, there’s a chance that things will stick together, as long as they don’t get degraded by radiation or oxidation,” says Sephton.

Earth lacks a geological file for when the constructing blocks of life first appeared, however Mars does have a rock file from that interval. “This is a giant experiment for polymerising organic matter and self-organising it, and it’s all preserved,” says Rapin.