Southwest Research Institute (SwRI) News

U.S.-built instrument to fly aboard ESA Mars Express

San Antonio, Texas -- May 28, 2003 -- The Mars Express spacecraft, set to launch June 2 from Kazakhstan, carries one of the most advanced electron spectrometers ever built as a component of the Analyzer of Space Plasma and Energetic Atoms (ASPERA) instrument flying aboard the craft. Built by Southwest Research Institute® (SwRI®), the electron spectrometer, along with ion composition and energetic neutral atom imaging components, will help characterize Mars' immediate space environment and study its interaction with the neutral gases of the martian upper atmosphere.

Understanding these interactions enables planetary scientists to characterize the present state of the martian atmosphere and to reconstruct its history and evolution over the past 3.5 billion years.

"The fact that Earth can maintain life is a unique condition in the solar system," says Dr. David A. Winningham, ASPERA co-investigator and an Institute scientist in the SwRI Space Science and Engineering Division. "Mars Express could tell researchers what variables are needed to first create, then preserve over geological time, oceans and atmospheres."

NASA provided funding to SwRI to build the electron spectrometer, which will measure electron fluxes in the energy range of a few to 20,000 electron volts, for the European Space Agency mission. The Swedish Institute of Space Physics in Kiruna, Sweden, leads the development of ASPERA in collaboration with researchers from Finland, Italy, England, Germany and France.

A strong planetary magnetic field helps maintain the atmosphere on Earth by shielding it from the solar wind - the hypersonic stream of charged particles that flows out from the sun. Without this magnetic shield, ionized gases in the Earth's upper atmosphere would be swept away, leading to a significant loss of atmospheric material over geologic time. Mars has no intrinsic magnetic field, or at best only a very weak one, leaving its atmosphere unprotected from erosion by the solar wind.

ASPERA will acquire data on the charged particles that impinge on the martian atmosphere and on the atmospheric material that is lost as a result of interactions with the solar wind. Recent theoretical calculations suggest that the oxygen lost by these and other processes over the last several billion years is equivalent to the amount of oxygen in a global layer of water about 50 meters deep. The ASPERA measurements could help determine whether liquid water, the primary requirement for life as we understand it, was ever present on Mars in significant amounts.

The spacecraft, and the ASPERA instrument in particular, will collaborate with the Japanese spacecraft Nozomi, which is also set to investigate the martian ionosphere and atmospheric loss. Measurements taken during Nozomi's equatorial orbit will complement those of Mars Express' polar orbit.

For more information about the ASPERA instrument and Mars Express, visit www.aspera-3.org and http://sci.esa.int/marsexpress/.