Investigating global scale dust storms on Mars with ASPERA-3

Abstract

2007 and 2018 saw global scale dust storms engulfing the entirety of Mars, lasting several months. These events have a profound impact across Mars, with dust reaching altitudes up to 80 km and global temperatures rising by up to 40 K. This significant change in the Martian atmosphere may lead to changes in the ionosphere and above. During the 2007 storm, it was seen in Mars Express (MEx) radar data that ionisation created in the lower atmosphere is observed at higher altitudes, with an altitude dependent enhancement in plasma density over crustal magnetic fields (Venkateswara et al., 2019). It may be likely that during these dust events, atmosphere loss is enhanced.MEx launched in 2003, became operational in 2004 and is still collecting data today. Onboard are seven scientific instruments which are answering questions about the atmosphere, surface and geology at Mars, whilst looking for signs of water and life. With a period of seven hours, MEx provides extensive coverage of data collection. One of the seven instruments, the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) has produced a long time-base of plasma measurements from as low as 250 km. ASPERA-3 aims to investigate the interaction of the solar wind with the Martian atmosphere, looking at the mechanisms that may enhance the loss of gases from Mars.ASPERA-3 will be used to investigate the effects the 2007 and 2018 global dust storms had on the plasma environment by comparing data before, during, and after the event.  Of particular interest are plasma measurements over radial magnetic fields from crustal anomalies, where transport of charged particles is guided out of the atmosphere.  The before, during, and after effects will shed light on to the influence dust storms have on the escaping plasma measured by ASPERA-3 and how dust changes the local plasma escape directly from the atmosphere. Our initial study focuses on data from the electron spectrometer (ELS) where we investigate how the energy distribution and peak energy value varies in altitude above the Martian surface. We will also relate our observations back down to the Martian surface, where we will investigate how surface features may influence the atmosphere and ionosphere above them. This will focus on the southern hemispheric crustal fields and geological features, such as impact basins and volcanoes.