College of Engineering, Design & Computing Events

Scott Thaller, PhD
Research Scientist
Laboratory for Atmospheric and Space Physics
University of Colorado Boulder

Abstract
In the distant past (billions of years ago) Mars had an abundance of surface water.  Images taken both by satellites and rovers have documented numerous surface features indicative of flowing water having been present at one time.  Today, however, Mars appears to have much dryer conditions than those needed to produce such features.  While water is still present on Mars, it is mainly frozen in the polar caps and frozen in and under the regolith.  Observations of isotopic ratios in Mars’ atmosphere, surface rock, as well as meteorites of Martian origin, indicate that a large quantity of the atmosphere and water originally on Mars has escaped to space.  The dominant mechanism(s) by which this happens are not fully understood.  Furthering our understanding of how Mars lost most of its atmosphere and water is the main goal of NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) mission.  MAVEN is equipped with instrumentation and an orbit well suited to measure Mars’ neutral upper atmosphere, ionosphere, and the solar wind plasma flowing around Mars.  The data collected by MAVEN since its arrival at Mars in September of 2014 has significantly advanced our knowledge of the planet’s atmosphere, ionosphere, and its interaction with the space environment.  In this talk I will briefly review the history of missions to Mars, focusing on the evidence they have provided for the presence of greater quantities of liquid water and thicker atmosphere in the past. I will then discuss how MAVEN is furthering our understanding of the evolution of Mars’ atmosphere.  In particular I will focus on MAVEN’s Langmuir Probe and Waves (LPW) instrument.  LPW enables us to determine the altitude profiles of electron temperature and electron density in the Martian ionosphere.  Such measurements are of critical importance to understand how the solar wind interacts with the atmosphere and ionosphere at higher altitudes and in determining the rates of chemical reactions at lower altitudes.  In addition, the electron temperature and density profiles provide important constraints for models of the Martian ionosphere-thermosphere system. The direct importance of MAVEN LPW measurements for understanding the evolution of Mars’ atmosphere will be explained. 

Bio. 
Dr. Thaller finished his doctorate program in 2014, at the University of Minnesota Twin Cities, after which he did four years of post-doctoral work in space plasma physics at the same institution.  In August of 2018 he joined the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder, as a research scientist.  Dr. Thaller’s research areas include measurements of the electric field in space plasmas, the plasmasphere and its dynamics, particle transport and energization in the inner magnetosphere, the Martian ionosphere, and plasma density determination from both spacecraft potential and from Langmuir probe measurements.

Email Address: Scott.Thaller@lasp.colorado.edu