Earth and Mars Share Similar Wet and Dry Seasons

The NASA Curiosity rover has discovered patterns in Mars’ mud that indicate seasonal weather on the red planet, similar to what Earth experiences. This suggests that Mars may have had alternating wet and dry seasons, potentially playing a role in the formation of complex building blocks for life, such as RNA and basic proteins.

While there is evidence of past liquid water on Mars in the form of lakes and rivers, scientists were uncertain if these were isolated events or part of a larger global weather cycle. However, William Rapin and his colleagues at the University of Toulouse, France, have analyzed images from Curiosity and identified a distinct pattern of hexagonal ridges in the mud of the Gale crater, a former lake. They believe these ridges could only have formed from repeated wet and dry environments, each lasting a Martian year or less.

Rapin states, “It’s the first time we can show that the climate sustained hydrological change seasonally, or wet and dry seasons. 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 propose that the ridges were originally cracks in the mud that eventually dried out. Flooding and mineral deposits would have filled in these cracks, and although some material would have been washed away, a mixture of mud and rock would have remained, giving rise to the hexagonal ridges we observe today. Rapin adds, “Only a seasonal climate – something with high frequency, geologically speaking – can produce those cracks in the mud that got fossilized.”

The estimated 4-centimeter-wide hexagons indicate a water depth of about 2 centimeters, suggesting regular cycles lasting around a Martian year and potentially persisting for millions of years.

Similar patterns can be found in certain environments on Earth, such as Racetrack Playa in California, which remains dry most of the year but fills with a shallow layer of water during the rainy season.

These rock formations on Mars are approximately 3.6 billion years old, around the same time life first emerged on Earth. This raises the possibility that life could have also emerged on Mars. Mark Sephton, a researcher at Imperial College London, suggests, “If you have life on Earth, then why not life on Mars, if conditions on both planets were about the same?”

The seasonal weather on Mars could have played a role in the formation of essential molecules for life, such as RNA and proteins. These molecules are built from organic matter, such as amino acids and nucleotides. Laboratory experiments have shown that the chemical reactions involved in creating these molecules often require periods of dehydration.

Sephton explains, “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.”

While Earth lacks a geological record of when the building blocks of life first appeared, Mars has preserved a rock record from that time. Rapin describes Mars as a “giant experiment for polymerizing organic matter and self-organizing it.”