Saturday, December 10, 2022

Study deepens mystery behind Mars’ arid climate

On Earth, several forces have worked together to keep conditions remarkably stable for millions of years. But other planets may not be so lucky. One of the many questions scientists have about other planets is how lucky we are—that is, how often this confluence exists in the universe.

Studying what happened to other planets like Mars could provide clues about planetary climates and how many other planets may be habitable.

Mars is the only world whose surface has become uninhabited. From 3.6 to 3.0 billion years ago the climate of Mars was at least sometimes warm enough to have rivers and lakes. We can estimate this as a habitable climate. But the surface today is a cold desert. Some constraints exist on the atmospheric greenhouse effect of Mars during the wet to dry transition.

Was early Mars temperate or icy, was the environmental catastrophe sudden or gradual, and what caused the change?

The prevailing view is that the drying up of Mars is due to atmospheric CO. had a loss2, The atmosphere of Mars today is so thin that it is close to the triple point of water, so lakes on early Mars probably formed in a dense atmosphere. CO2 In the modern inner solar system, climate change is a major greenhouse gas to control.

But new research findings, published in the journal Science Advances on May 25, 2022, suggest that the change was caused by the loss of some other important component, which kept the planet warm enough for running water.

“People have put forward different views, but we’re not sure what causes such a dramatic change in climate,” said Edwin Kite, a geophysicist at the University of Chicago. “We really want to understand, especially because it’s the only planet we know has definitely changed from habitable to uninhabitable.”

Kite is the first author of a new research study that examines the tracks of Martian rivers to see what they may reveal about the history of the planet’s water and atmosphere.

“However, even when H2O vapor reaction is assumed, the addition of non-CO2 Warming is needed to warm Mars enough for rivers. Therefore, non-CO . change in2 Radiation forcing is an alternative explanation for Mars’ wet-to-dry transition. The relative importance of these mechanisms has not been investigated, so the prevailing interpretation of the wet-to-dry transition has not been tested,” the study mentions.

From having water everywhere to not even a drop of water: what did the researchers analyze?

For Years, Researchers Have Debated Whether Mars Once Had Enough Water To Form An Ocean, As Depicted In This Concept Illustration.
For years, researchers have debated whether Mars once had enough water to form an ocean, as depicted in this concept illustration. credit: NASA/GSFC

In 1972, scientists were astounded by photographs of NASA’s Mariner 9 mission as it orbited Mars from orbit. The photos revealed a landscape filled with riverbeds, evidence that the planet once had lots of liquid water, even though it’s dry as a bone today.

Since Mars does not have tectonic plates to move and bury the rock over time, ancient river tracks still lie on the surface as evidence of hastily discarded.

This allowed Kite and his colleagues, University of Chicago graduate student Bowen Fan as well as scientists from the Smithsonian Institution, the Planetary Science Institute, the California Institute of Technology Jet Propulsion Laboratory and Aeolis Research, to analyze maps based on thousands of photographs. . orbit by satellites. Based on which tracks overlap, and how they are weathered, the team pieced together a timeline of how river activity changed in altitude and latitude over billions of years.

They can then combine this with simulations of different climate conditions, and see which matches best.

Planetary climates are very complex, involving many variables.

The heat can come from a planet’s sun, but it has to be close enough to receive radiation but not so close that the radiation washes away the atmosphere. Greenhouse gases such as carbon dioxide and methane can trap heat near a planet’s surface. Water also plays a role; It can exist in the form of clouds in the atmosphere or as snow and ice on the surface. Snowcaps act as mirrors to reflect sunlight back into space, but clouds can either trap or give away light depending on their height and composition.

Kite and his colleagues ran several different combinations of these factors into their simulations, looking for conditions that would warm the planet enough to exist in at least some liquid water rivers for more than a billion years and Then suddenly lose it.

After comparing different simulations, he noticed something surprising. Changing the amount of carbon dioxide in the atmosphere did not change the result. That is, the driving force of change did not seem to be carbon dioxide.

“Carbon dioxide is a strong greenhouse gas, so it was actually the prime candidate to explain the drying out of Mars,” said Kite, an expert on otherworldly climates. “But these results show that it is not that simple.”

There may be various possibilities which the study summarizes.

“Our analysis shows that changes in river distribution were driven by the loss of non-CO2 Radiation force. Subsequent cessation of river-forming climate on Mars may be due to further reduction in non-CO2 H. by greenhouse warming2O loss, or by loss. The current rate of C escape into space is low, and isotopic evidence indicates that much of Mars’ atmosphere >3.5 Ga was previously lost. Candidate carbon sinks include space escape, carbonate formation, and CO. involves basal melting of2 ice. Alternatively, CO2 CO. could be indexed inversely as2 Snow.” The study mentions.

What will happen next?

“We don’t know what this factor is, but we need it very much to interpret the results,” Kite said.

There are several ways to try to narrow down the possible factors; The team suggests several possible tests for the performance of NASA’s Persistence rover that may reveal clues.

Kite and colleague Sasha Warren are also part of the science team that will direct NASA’s Curiosity Mars rover to search for clues about why Mars dried up. He hopes that these efforts, as well as measurements of persistence, may provide additional clues to solving the mystery.

“It’s really amazing that we have this puzzle next door, and yet we’re still not sure how to explain it,” Kite said.

journal reference

  1. Edwin S. Kite, Michael A. Mishnah, Bowen Fan, Alexander M. Morgan, Sharon A. Wilson, Mark I. Richardson. Changes in the spatial distribution of water flow charts Major changes in the greenhouse effect of Mars. science advanceVolume 8, Issue 21 DOI: 10.1126/sciadv.abo589

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