Nightly Snow on Mars


Although entrepreneurs and movie directors like to imagine humans inhabiting the red planet, in reality scientists study Mars because they want to find out more about Earth. In particular, scientists want to better understand Mars’ atmosphere. A recent experiment has scientists excited about the role of wind and ice in the planet’s atmospheric dynamics.

Modern day Earth has many features in common with ancient Mars. A thick atmosphere and rain clouds were part of Mars’ past. Scientists want to understand what occurred to give rise to modern day Mars’ thin atmosphere, cold temperatures and scarce water. One probe that offered some insight into the planet’s current atmosphere was NASA’s Phoenix Mars Lander that recorded signs of snowfall. At the time, scientists believed the snowfall was only a small accumulation that had been built up over time and was therefore negligible. The information was recorded but not investigated until recently.

Planetary scientist Aymeric Spiga decided to investigate the snowfall. Using more recent data from NASA’s Mars Reconnaissance Orbiter and Mars Global Surveyor Spiga and his colleagues noticed wind patterns that increased after the sun went down. Without the warmth of the sun, Mars’ thin climate reacts much more quickly and with more intensity than the Earth’s atmosphere. The rapidly cooling surface, combined with water-ice clouds, produced lots of wind. Using a temperature model, Spiga and team recreated the Martian atmosphere and concluded that “snow” fell every evening. But Martian snow is not like earth snow. Rather, the snow is more like chunks of ice falling at the speed of an Earthly thunderstorm.

Because of the limited supply of water the accumulations are small. Although they may have appeared to earlier scientists as a slow accumulation, Spiga determined that the snow falls regularly. But the study’s importance isn’t entirely centered around cold precipitation. The scientists are investigating the intensity of Martian wind and the dynamics of the Martian atmosphere.

The atmosphere on Mars has diverged from the atmosphere on Earth for reasons that might have to do with a shift in the planet’s axis. Prior to the shift, the poles experienced more sunlight. Understanding the atmosphere’s reaction to this change in heat and light can help scientists determine the role temperature plays in climate. Though this recent discovery doesn’t answer all of the questions regarding Mars’ chaotic tilt it is one more clue in solving the mystery.


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