ASPERA-3: Next Stop Mars
Picture of the Mars Express
Mars Express
ASPERA-3 is one of the scientific instruments that will fly aboard Mars Express. The scientific objectives of ASPERA-3 are to study the interaction between the solar wind and the atmosphere of Mars and to characterize the plasma and neutral gas environment in the near-Mars space. The instrument will use a technique known as Energetic Neutral Atom (ENA) imaging to visualize the charged and neutral gas environments around Mars. ASPERA-3 will make the first ever ENA measurements at another planet. These studies will address fundamental questions directly related to the many unknowns about water on Mars.

ASPERA stands for Analyzer of Space Plasmas and Energetic Atoms. The "3" denotes that this is the third ASPERA instrument to fly to Mars. ASPERA on board the Russian Phobos 2 mission in 1988 did an excellent job. ASPERA-C on the Russian Mars-96 mission has never been heard from since it lies at the bottom of the Pacific Ocean together with the ill-fated spacecraft, due to a malfunction during the third revolution around the Earth. Investigators are looking to ASPERA's third journey to Mars to add a new piece in the Martian water puzzle.

The ASPERA-3 experiment will allow scientists to study the interaction between the Martian atmosphere and solar wind, charged particles streaming away from the Sun. They hope to learn how strongly the interplanetary plasma and electromagnetic fields affect the Martian atmosphere. This question is directly related to the problem of where the Martian water has gone. As the water on the surface evaporates, the vapor reaches the upper atmosphere and the water molecules can break apart, forming molecules of hydrogen and oxygen. The atoms can then be ionized and eventually be picked up by the solar wind. It is not clear how effective this process is. Scientists want to find this out and to determine the fate of the Martian water.

The ASPERA-3 instrument has four sensors to gather the data, along with the data processing unit and the scanning platform (see illustration). Two of the sensors, the Electron Spectrometer (ELS) and the Ion Mass Analyzer (IMA) Imaging Detector, are being funded by NASA as a Discovery Mission of Opportunity. The IMA is a separate unit connected by a cable to the ASPERA-3 experiment.

  • Ion Mass Analyzer (IMA) will measure ion fluxes from all directions in the energy range from a few electron volts up to 40,000 electron volts.

  • Electron Spectrometer (ELS) will make measurements of the electron fluxes in the energy range from a few electron volts up to 20,000 electron volts. This may be the smallest electron spectrometer ever built.

  • Neutral Particle Imager (NPI) combined with the Neutral Particle Detector (NPD) will measure energetic neutral atoms (ENA) in the energy range between 100 and 10,000 electron volts, providing a complete range of data about global distribution of plasma around Mars.

Picture of David W.
David Winningham
Dr. Rickard Lundin of the Swedish Institute of Space Physics led the development of ASPERA-3. The ELS and IMA were built by Southwest Research Institute of San Antonio, Texas, led by David Winningham, Principal Investigator and John Scherrer, Project Manager. The instrument is being built by a large international team of 15 groups from 10 countries.

A Discovery Mission of Opportunity is not a complete Discovery Mission, but rather one piece of a larger mission. It gives the U.S. scientific community the chance to participate in missions of non-U.S. government agencies by providing funding for a science instrument, hardware components of a science instrument, or expertise in critical areas of a mission.