UC Berkeley instruments shed light on Mars climate change mystery

Four science instruments designed and built at UC Berkeley’s Space Sciences Laboratory (SSL) provided key data to help NASA’s MAVEN mission determine the present rate at which Mars is losing its atmosphere to space.

The measurements from the Mars Atmosphere and Volatile Evolution mission suggest that the loss rate was much greater billions of years ago, when the sun was more active and the solar wind stronger. The loss of atmospheric gases – primarily hydrogen and oxygen – appears to have been one of the main reasons the Martian climate went from an early, warm, wet one that might have been able to support life at the surface to the cold, dry, desert planet we see today.

The first scientific results from the MAVEN mission are being published online Nov. 5 in the journals Science and Geophysical Research Letters.

The UC Berkeley instruments measure charged particles (electrons and electrically charged gas atoms called ions) as MAVEN orbits Mars, dipping into its upper atmosphere once per orbit. The combined measurements from these and MAVEN’s five other instruments have demonstrated that the solar wind is able to strip away gas at a rate of about 100 grams (equivalent to roughly one-quarter pound) every second.

The solar wind is a stream of particles (mainly protons and electrons) coming out from the sun’s atmosphere at a speed of around a million miles per hour. Because the solar wind carries a magnetic field with it, it is able to accelerate ions in Mars’ upper atmosphere and remove them to space. MAVEN results have shown that loss comes from three different regions around the planet: above the Martian poles in a “polar plume,” down the “tail” where the solar wind flows behind Mars, and from the extended cloud of gas that always surrounds Mars.

The instrument that measured this ion flux was the SupraThermal And Thermal Ion Composition (STATIC), built at SSL.

“We designed STATIC to be sensitive enough to measure ions escaping from Mars over a wide range of masses, energies and fluxes,” said UC Berkeley’s.James McFadden, who is the lead scientist for the STATIC Instrument. “This data is essential to MAVEN’s objective of characterizing ion loss from the Martian atmosphere.”

UC Berkeley’s Space Sciences Laboratory plays a major role on the MAVEN mission. A team of more than 20 SSL engineers and scientists designed and built the four instruments mentioned above. In addition to STATIC, the other Berkeley instruments are SEP (Solar Energetic Particles), led by Davin Larson; SWEA (Solar Wind Electron Analyzer), led by David Mitchell; and SWIA, led by former SSL scientist Jasper Halekas.

SSL also designed and built two 7-meter-long deployable booms for a sensor called a Langmuir probe that measures temperatures and densities of electrons, and a flight computer that controls and collects data from seven of MAVEN’s nine science instruments.

Currently a team of a dozen UC Berkeley scientists led by MAVEN’s deputy principal investigator Janet Luhmann is actively involved in analysis of all MAVEN data.

MAVEN has been operating at Mars for just over a year, and is about to complete its primary science mission on Nov. 16. The mission has been approved for a 10.5-month extended mission through September 2016. The spacecraft and instruments continue to operate nominally.