Research Assistant Professor Christopher Fowler is a planetary science researcher in the West Virginia University Department of Physics and Astronomy and the Center for KINETIC Plasma Physics. Fowler analyzes in-situ plasma measurements obtained by spacecraft, including the NASA Mars MAVEN (Mars Atmosphere and Volatile EvolutioN) mission, where he works on the instrumentation team.
He works to understand the physical processes that energize the ionospheres of unmagnetized planets — planets lacking a magnetic field — such as Mars and Venus. His research focuses on electromagnetic forces, or plasma physics, and how they play a role on Mars.
Fowler and the NASA MAVEN team worked alongside the European Space Agency Mars Express mission team to publish their findings in Nature, describing the destructive nature of solar wind as it pertains to Mars and how it affects Mars' evolution as a planet.
The team combined observational data from both Mars missions with extensive computer simulations to understand how solar wind affects the red planet. The simulations found unexpected answers related to the condition of Mars' atmosphere; or at least what’s left of it.
Our Sun emits a continuous stream of charged particles out into our solar system. This stream is known as solar wind, or stellar wind. As the solar wind encounters the planets in our solar system, a variety of physical forces act to try and deflect this flow around them, protecting the planets from solar wind damage. Solar wind carries with it a magnetic field that originates from the Sun. The orientation and strength of this magnetic field are known to play important roles in how planets deflect solar wind. Interactions between planets and stellar winds can spur atmospheric loss which is a critical factor in the evolution of planets. Planets in our solar system normally interact with solar wind, but those planets without a magnetic field, like Mars, react and adjust very differently.
Fowler and team found that when the solar wind magnetic field was aligned in a unique orientation, interesting things happened in the space environment around the planet.
Under normal conditions at Mars upon arrival of solar wind, the planet’s atmosphere is able to deflect most of the solar wind, offering protection (this happens despite Mars lacking its own magnetic field). But this, as it turns out, is not always the case. Fowler notes “In this unique case, the solar wind essentially “crashed into Mars”, rather than being deflected around it, as happens under normal conditions.”
“It’s thought that this “crashing into Mars” may help to strip significant chunks of the atmosphere off into space,” Fowler says. “These unique conditions also occur at other planets in our solar system, making them an important process to understand, if we wish to understand how our star and others in our galaxy interact with objects in their solar systems.”
Scientists know there was once liquid water on the surface of Mars because of the abundance of geological features seen on the surface: dried out river beds, lakes and seas that can only be formed by flowing liquid water at some point in Mars’ past. The presence of liquid water indicates that Mars also once had a dense atmosphere that would keep the planet warm enough to allow water to flow on the surface. Mars is also thought to have had its own magnetic field at some point in the past, which it subsequently lost. Thus, over millions of years, the solar wind has been able to slowly erode the planet’s atmosphere to space, and is thought to be one of the reasons why Mars’ atmosphere is over 100 times thinner than that of Earths.
The unique conditions investigated in this study likely represent “extreme cases” of this erosion. “While these unique solar wind conditions don’t happen very often at Mars today, we think they were much more frequent in the past (millions of years ago) when our Sun was younger and more active. What’s particularly exciting for me to think about is that the solar wind could have been crashing into Mars on a daily basis, rather than the couple of times a year that it experiences at present.”
Conditions on Mars, as it exists today, are vastly different from its past and scientists want to understand how these extreme conditions and processes have affected its evolution and will continue to shape its future.
“The combination of spacecraft observations and computer simulations can be a powerful research tool, allowing us to shed light on how, in this case, Mars has evolved over the 4 billion year history of the solar system. What’s particularly exciting is to think about the thousands of planets now being detected outside our galaxy by astronomical telescopes. We won’t get to send spacecraft to those planets any time soon: the travel time from Earth with current technology would be hundreds if not thousands of years. However, we can apply what we know about our Sun and the planets in our solar system to those far away solar systems: what might they look like and how might they interact together?”
hal/10/01/24