• Introduction
    • Aspera



      ASPERA-3 (Analyzer of Space Plasma and Energetic Atoms) is one of seven scientific instruments aboard the orbiting Mars Express spacecraft that are performing remote sensing measurements designed to answer questions about the Martian atmosphere, structure, and geology. ASPERA-3 is measuring ions, electrons and energetic neutral atoms in the outer atmosphere to reveal the number of oxygen and hydrogen atoms (the constituents of water) interacting with the solar wind and the regions where such interaction occurs.


      Mission Management

      Dr. David Winningham
      Dr. David Winningham,
      Principal Investigator

      The ASPERA-3 instrument was built by a large international team of 15 groups from 10 countries. The NASA-funded components, the Electron Spectrometer and the Ion Mass Analyzer Imaging Detector, were built by Southwest Research Institute of San Antonio, TX, led by Dr. David Winningham, Principal Investigator.

  • Science Objectives
    • 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 uses a technique known as Energetic Neutral Atom (ENA) imaging to visualize the charged and neutral gas environments around Mars. ASPERA-3 is making the first ever ENA measurements at another planet.

      These studies will address the fundamental question of how strongly interplanetary plasma and electromagnetic fields affect the Martian atmosphere, which is directly related to the many questions about water on Mars. Since liquid water is the key requirement for life, a clear understanding of the fate of Martian water is crucial to resolve whether or not life existed on Mars in the past.

      Depiction of the components of the ASPERA-3 instrument.
      Depiction of the components of the ASPERA-3 instrument.
  • Details

      Mars Express is a European Space Agency mission that launched from Russia on June 2, 2003, and entered into orbit around Mars on December 25, 2003. It is Europe’s first mission to Mars.

      Constant bombardment by the stream of charged particles pouring out from the Sun is thought to be responsible for the loss of Mars's atmosphere. The planet no longer has a global magnetic field to deflect this solar wind, which is consequently free to interact unhindered with atoms of atmospheric gas and then sweep them out to space. ASPERA-3 will detect this plasma escaping the planet and allow scientists to estimate how much atmosphere has been lost over billions of years.

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


      Assembled view of the ELS sensor.
      Assembled view of the ELS sensor.
  • Results
    • ASPERA-3 has made a number of interesting new discoveries and contributed greatly to our understanding of the Mars plasma environment.  Most of the findings are on the solar wind interaction with Mars, its ionosphere and atmosphere, but one of them relates to the generation of ENAs in interplanetary space.  These findings and their related consequences are summarized as follows:
      — The solar wind plasma may penetrate deep into the dayside ionosphere and atmosphere, leading to strong solar wind forcing and the acceleration and outflow of planetary ions.
      — Despite the lack of a strong intrinsic magnetic field, the low-altitude ion energization and outflow from Mars are surprisingly similar to the ion energization and outflow over Earth.
      — The distribution of the planetary wind ions suggests two major acceleration processes:  direct solar wind energy and momentum exchange and ‘auroral plasma’ acceleration processes.
      — Observations of plasma acceleration, ions upward and electrons downward, in confined cusp-like regions near local midnight confirm the existence of an ‘equatorial aurora’ at Mars.

      The ASPERA-3 ENA instruments have also made it possible to study completely new aspects of the solar wind interaction with an unmagnetized planet. Detailed results can be found in “Mars Express: The Scientific Investigations,” ESA special publication SP-1291, June 2009.

      Mars Express orbits the Red Planet in a highly elliptical, polar orbit that brings it close to the moon Phobos every five months.  It is currently the only spacecraft whose orbit reaches far enough from the planet to provide a close-up view of Phobos.

      Like our Moon, Phobos always shows the same side to the planet, so by flying outside the orbit it becomes possible to observe the far side. During a flyby campaign in February and March 2010, all seven instruments onboard Mars Express were used to study Phobos.  Images from the flyby show Mars’ rocky moon in exquisite detail.

      This illustration shows the comet-like solar wind  interaction with Mars.  Details can be  found in ESA Special Publication SP-1291.
      This illustration shows the comet-like solar wind interaction with Mars.  Details can be found in ESA Special Publication SP-1291.

      This diagram shows the orbits of Phobos and  Mars Express
      This diagram shows the orbits of Phobos and Mars Express around Mars, with the point where the orbits cross indicated at top left. Credit: NASA/ESA

      Mars Express
      Phobos as seen by the High Resolution Stereo Camera on Mars Express, enhanced to bring out features in the less-illuminated part.
      Credit: ESA/DLR/FU Berlin (G. Neukum)
  • Noteworthy
    • Mars Express carried the Beagle 2 lander which was designed to determine the geology and the mineral and chemical composition of the landing site, to search for life signatures, and to study the weather and climate. On the December 19, 2003, five days before orbit insertion, the Beagle 2 lander was released toward the surface of the planet and contact was lost. It may have missed Mars, skipped off the atmosphere and entered an orbit around the Sun or burned up during descent. If it reached the surface, it may have hit too hard or failed to make ground contact due to a fault. Sadly, it joined the ranks of eleven other doomed Mars missions.

      Artist’s concept of Beagle 2
      Artist’s concept of Beagle 2's on its way through the Martian atmosphere, protected by a heat resistant shield. Its fate is unknown.