Mars’ Rust Indicates a Wet Past – And the Ocean is Frigidly Cold

Early beach days on Mars would not have made for a relaxing getaway.

Recent observations of the Red Planet have revealed potential ancient coastlines in its Northern Hemisphere. Another study indicates that the minerals present contribute to Mars’ distinctive reddish hue.

“You can envision early Mars as having abundant liquid water,” remarks Alberto Fairen, a hominologist not involved in either study. He is associated with the Center for Astrobiology in Madrid, Spain, and Cornell University in Ithaca, New York.

New research indicates that the ancient oceans on Mars would have been quite frigid. Fairen describes them as akin to a beach on the Arctic Ocean.

Ancient Coastline Discovered

Scientists believe that Mars was home to significant amounts of liquid water over 3 billion years ago. The low-lying northern areas could house vast oceans, forming a bowl-like depression compared to the rest of the planet.

In 2021, China’s rover landed on the region’s edge, using radar to search for signs of historical coastlines.

The rover discovered a sloped area approximately 10-35 meters (30-115 feet) below the surface, extending over 1.3 km (0.8 miles). This slope aligns closely with the characteristics of beaches on Earth. Radar data indicates that the slope consists of pebble and sand-sized particles.

The findings were published on February 24 in the Proceedings of the National Academy of Sciences.

The buried slope is unlikely to be a sand dune, as its features differ from wind-blown dune shapes found elsewhere on Mars. Furthermore, it does not show signs of having been shaped by rivers or lava flows, resembling instead Earth’s coastline.

While these data do not yet confirm the existence of a full-sized ocean on Mars, if the area represents an ancient coast, it could offer insights into whether life once thrived on the planet.

“The interface between water, rocks, and air provides a favorable environment for life,” says Michael Manga of the University of California, Berkeley, who participated in this study. He adds, “Some of the earliest life on the planet may have existed in such environments.”

Mars’ Famous Red Dust

The second study explores the nature of liquid water on Mars.

“We were essentially addressing the longstanding question of why Mars is red,” states Adam Valantinus, a planetary scientist at Brown University in Providence, Rhode Island.

The planet’s color is believed to originate from rust. “However, there are various types of rust,” Valantinus highlights. “Each type informs us about the environmental conditions under which rust forms.”

For years, scientists have suspected Mars’ rust to be hematite (Heem-uh-Tyte). Since this type of rust lacks water, it would have formed after the planet’s surface lost its liquid water. However, this presents a dilemma—Mars’ dust absorbs light differently than hematite and does not reflect it in the same way. Additionally, scientists have discovered other water-containing minerals on Mars’ surface.

This led Valantinus and his colleagues to reconsider whether hematite was responsible for Mars’ red tint.

In laboratory experiments, they measured how various minerals absorb and reflect light. This data was then compared to observations from Mars’ spacecraft and orbiters.

The mineral that best matches the Martian surface is a combination of ferrihydrite and basalt (Buh-Salt), a form of volcanic rock. These findings were published on February 25 in Natureral Communications.

Ferrihydrite is a type of rust that contains water. According to Valantinus, it likely required cold and damp conditions to form. On Mars, these minerals are somewhat unstable, gradually transitioning to a more stable form (like hematite). However, a cold, acidic environment could slow this process, allowing the ferrihydrite to remain stable until liquid water disappeared.

Source: www.snexplores.org