NASA’s Curiosity Mars rover is now sending back weather reports and radiation measurements. Using the Rover Environmental Monitoring Station (REMS) instrument built by Spain’s Centro de Astrobiologia (CAB), the nuclear-powered robot has been taking measurements of atmospheric pressure, temperature, wind speed and other factors to better understand the Martian environment in hopes of finding out whether life could still exist on the Red Planet.

Located on Curiosity’s camera mast, the REMS was built to be particularly rugged because it’s constantly exposed – a point that was made clear when the rover landed on August 6 and one of the REMS’s wind sensors was damaged. Since then, Curiosity has analyzed 20 atmospheric events as it builds up a detailed picture of Martian weather in Gale Crater.

Diagram of the Martian thermal tide (Image: NASA/JPL-Caltech/Ashima Research/SWRI)

Mars is a very strange and unpleasant place when it comes to weather. Because the atmosphere is only one one-hundredth that of Earth, the weather goes through dramatic cycles each day and as the Martian seasons change. The temperature varies by 100 degrees Fahrenheit each day, and to extremes ranging from -199ºF (-128ºC) during the polar night to 80ºF (27ºC) at noon at the equator in summer.

This daily heating and cooling produces what are called “thermal tides” – the atmosphere expands into a pronounced bulge on the day side of the planet, that is 30 percent larger than the atmosphere on the night side. This bulge travels around the planet like a tide, hence the name. The pressure differences caused by these tides are spectacular. On Earth, such changes are seen solely during hurricanes, but the thin atmosphere of Mars makes them only detectable with instruments.

The Rover Environmental Monitoring Station (REMS) instrument being installed on Curiosity (Photo: NASA/JPL-Caltech)

The Martian air pressure also changes seasonally, as tons of carbon dioxide evaporate from the southern ice cap as the southern hemisphere spring becomes summer. All of this has a direct bearing on Curiosity’s two-year mission to seek out places where life may have or might still exist on Mars. These changes in air density affect many other factors, such as the amount of dust in the air – and as the air expands, it becomes less dense, letting in more cosmic and UV radiation. These types of radiation are inimical to life and reduce the chances of it existing on the surface of Mars. It also will affect future explorers who might visit the planet during manned missions. For this reason, monitoring radiation levels is particularly important.

One development in Curiosity’s weather monitoring is the detection of whirlwinds or dust devils. These have been seen by other NASA Mars rovers and from orbit, but not by Curiosity. The 4x4-sized explorer detected these by means of brief changes in pressure, wind direction, wind speed, UV radiation and temperature in the vicinity. Scientists at mission control at the Jet Propulsion Laboratory (JPL) in Pasadena, California believe that a lack of fine dust being picked up by the dust devils may be the reason why none have been seen.

Martian weather for November 14, 2012 (Image: CAB)

"Dust in the atmosphere has a major role in shaping the climate on Mars," said Manuel de la Torre Juarez of JPL. “The dust lifted by dust devils and dust storms warms the atmosphere."

Another enigma being studied is the winds in the vicinity of Curiosity, which blow mainly east-west. JPL scientists believe that this may be due to the shape of Gale Crater. "With the crater rim slope to the north and Mount Sharp to the south, we may be seeing more of the wind blowing along the depression in between the two slopes, rather than up and down the slope of Mount Sharp," said Claire Newman, a REMS investigator at Ashima Research in Pasadena. "If we don't see a change in wind patterns as Curiosity heads up the slope of Mount Sharp – that would be a surprise."

The video below is supplied by JPL and provides more details on Curiosity's weather and radiation monitoring.

Source: NASA

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