By Charlene Porter
After more than three months on Mars, the rover Curiosity is using its scientific instruments to give Earth-bound scientists a view of the changing seasons on the Red Planet
The rover carries 10 sophisticated instruments — known together as the Mars Science Laboratory (MSL) — and they’re providing data on atmospheric pressure and radiation conditions that lead scientists to describe the Martian environment as “dynamic.” In a November 15 briefing from mission control, Ashwin Vasavada, MSL deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, described what it would be like standing next to the rover at a site known as Gale Crater.
“You’d realize you were on a planet with an atmosphere, an atmosphere that’s thick enough that when the sun heats the ground every day, gusty winds rush up and down the slopes of Gale Crater and Mount Sharp and spawn whirlwinds that sweep across the landscape.”
But the atmosphere would not be thick enough to shield you from the radiation beating down on the planet from space, Vasavada warned. That’s important information, critical to assessing the needs and the precautions for a future human crew that might set down on Mars.
“The radiation is a life-limiting thing to habitability,” said Don Hassler, the principal investigator of the radiation assessment detector on MSL. “We need to understand what the radiation is doing if we want to understand the prospects for current, present and past habitability.”
The primary mission for MSL is to assess habitability of Mars and detect environments where microbial life may have survived. Decades of observations from orbiters and previous rovers have led scientists to conclude that Mars was once a wet, warm planet, though now it is cold and dry. Gathering data to better understand how the transition of the planet occurred is also a part of the mission.
Just as the seasons have changed here on Earth since Curiosity first touched down in August, the rover’s instruments are also detecting signs of a changing season. The Rover Environmental Monitoring Station (REMS) monitoring air pressure has tracked notable variations in atmospheric pressure, following both a pattern of seasonal increase and a daily rhythm of rising and falling.
The seasonal increase in air pressure results from tons of carbon dioxide vaporizing out of the southern winter ice cap that retreats with the onset of the Martian spring, explained Claire Newman, another investigator monitoring the REMS data at ASHMA Research Pasadena, a private research group collaborating with JPL on the Curiosity mission.
“The signature of the entire Martian atmosphere [is] growing in size as we move into springtime in the southern hemisphere,” she said, which is a phenomenon ”unlike anything we see on Earth.”
Newman said the scientific team has calculated that the Martian atmosphere shrinks and grows by about 30 percent as it moves through this seasonal transition.
REMS is also measuring daily changes in atmospheric pressure of about 10 percent, she said, a variation caused by the sun’s warming and cooling the atmosphere through a sol, a Martian day, which is about 40 minutes longer than a day on Earth..
“By measuring the pressure in just this one location on Mars,” Newman said, “we can learn a lot about what’s going on across the entire planet.” The better scientists understand present-day atmospheric changes on Mars, the better they will be able to project backward and theorize planetary conditions of the past, she said.
The scientists also noted that the findings regarding radiation and atmospheric pressure on Mars represent the most detailed data ever collected from another planet.
Curiosity has successfully collected and studied a couple of soil samples, and while all the data are not yet completely analyzed, initial experiments show the mineralogy of Martian soil is similar to weathered basaltic soils of volcanic origin in Hawaii.