Curiosity finishes second Martian year with weather report
NASA’s Curiosity Mars rover completed its second Martian year at Gale Crater on Wednesday, May 11. The mission’s science team commemorated this important milestone by issuing a weather report of the rover’s observations of two full cycles of Martian seasons. Having data on at least two seasonal cycles on Mars helps to distinguish seasonal effects from sporadic events.
Curiosity’s Rover Environmental Monitoring System (REMS), provided by Spain’s Centro de Astrobiologica, has measured air temperatures ranging from 60.5 degrees Fahrenheit (15.9 °C) on a summer afternoon to minus 148 degrees Fahrenheit (–100 °C) on a winter night. In addition to temperature, Curiosity also measured water vapor and atmospheric pressure.
“Curiosity’s weather station has made measurements nearly every hour of every day, more than 34 million so far,” said Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory, Pasadena, California. “The duration is important, because it’s the second time through the seasons that lets us see repeated patterns.”
Because Mars is farther away from the Sun than the Earth is and takes longer to complete one orbit around the Sun, one Martian year lasts 687 Earth days. Mars has a tilt similar to Earth’s, which contributes to having four seasons. Mars’ orbit is more elliptical than Earth’s, which results in longer and colder southern autumn and winter seasons than if the orbit were circular. This pronounced seasonal effect in the southern hemisphere is observable even at Gale Crater’s near-equatorial location.
“Mars is much drier than our planet, and in particular Gale Crater, near the equator, is a very dry place on Mars,” said Germán Martínez, a Curiosity science team collaborator from Spain at the University of Michigan, Ann Arbor. “The water vapor content is a thousand to 10 thousand times less than on Earth.”
Curiosity’s air pressure readings have confirmed a seasonal trend observed by previous missions. Carbon dioxide makes up most of the Martian atmosphere. During each pole’s winter, millions of tons of this gas freeze solid, only to be released again in the spring, resulting in seasonal variations of about 25 percent in atmospheric pressure.
Curiosity also measured changes in the concentration of methane in the air above Gale Crater using the tunable laser spectrometer in the rover’s Sample Analysis of Mars (SAM) suite of instruments.
For most of the two Martian years, the rover has measured methane concentrations between 0.3 and 0.8 parts per billion. For several weeks during the first autumn, the level spiked, reaching seven parts per billion. The mission checked carefully for a repeat of that spike during the second autumn, but concentrations stayed at lower background levels.
“Doing a second year told us right away that the spike was not a seasonal effect,” said JPL’s Chris Webster of the SAM team. “It’s apparently an episodic event that we may or may not ever see again.”
While continuing to monitor the current environment at Gale Crater, Curiosity is studying the geological layers of Mount Sharp to increase understanding of ancient changes in environmental conditions.
Video courtesy of NASA
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.