MAVEN: Where did the water go?
MAVEN is NASA's next Mars Scout that is currently en route to Mars to explore how the atmosphere is evolving and where the water content has gone. Specifically, MAVEN will determine how much of the Martian atmosphere has been lost over time by measuring the current rate of escape to space and gathering enough information about the relevant processes to allow extrapolation backward in time.
Mars lacks an intrinsic dipole magnetic field, so the upper atmosphere is directly exposed to the solar wind. Neutral atmospheric constituents in this region can be subsequently ionized and 'picked up' and swept away by the background convective electric field. This process is know as 'pick-up ion loss'. An important tool for interpreting pick-up ions in the MAVEN data is a model of Mars' atmosphere. The spacecraft cannot be everywhere at all times, so using sophisticated simulation techniques, global maps of pick-up ions can help fill in the gaps when the spacecraft is not able to observe a specific region.
The Mars Test Particle simulation (MTP) has been developed to study pick-up ions and ion transport through near-Mars space. It is a parallel 3-D Monte Carlo model that describes how Mars pickup oxygen ions are transported and accelerated once they are generated in the upper atmosphere and exosphere. Initial results from this model were presented and discussed in Fang et al. [2008, 2010a, 2010b], and Curry et al. [2013a, 2013b, 2014].
The magnetic and electric fields are calculated by a separate model and provide the background conditions for our test particle simulation. The test particle motion is followed by solving the Newton-Lorentz equation using a staggered leap-frog scheme. By monitoring the trajectories of a large number of test particles, we can obtain a global picture of how angular and energy spectra of pickup oxygen ions distribute in the Martian plasma environment and how a variety of ion sources play a role in the flux distribution.
Illustrations Copyright Lynnette Cook
Exoplanets: Can they really support life?
The atmospheres of exoplanets are critical in understanding if they are warm enough to support life and if the atmospheric pressure is enough to at least have liquid water or some other substance on the surface.
Exoplanets in the 'goldilocks' zone are not too close or not too far from the star they orbit so they maintain a surface temperature that could support life. But even if they are just the right distance from the star they orbit, their atmosphere is the next step to determining if they could support life. Planetary atmospheres not only absorb harsh radiation but also help keep a temperature balance. At Mars, the atmosphere has been escaping much faster than at Earth so it is tenuous and the atmospheric pressure is significantly lower. Liquid water would boil during the day and freeze at night so the conditions are extreme to sustain life. So understanding how the atmosphere of exoplanets are evolving is a huge piece of the puzzle in trying to see if there are other Earth-like planets out there, let alone other life.
Image courtesy of http://spaceweather.uma.es/solarstorms.html
Solar Energetic Particles (SEP)
Because Mars lacks an intrinsic global magnetic field, SEP ions can have near-total access to its upper atmosphere. Despite their episodic occurrences, SEP events provide an important source of energy input that can significantly affect the Martian atmosphere on a global scale, causing atmospheric loss and driving chemical reactions. Currently, our knowledge of SEP effects on the Martian atmosphere is limited because data (of both SEPs and their atmospheric effects) have been scarce and since appropriate modeling tools have not been applied to the problem in a comprehensive way. Currently, we are trying to characterize the rates of impact ionization, dissociation, excitation, and heating from simulations of ion transport throughout the Martian atmosphere
Venus: The densest terrestrial atmosphere and no magnetic field
The modeling of the atmospheres of unmagnetized bodies in the solar system is a complex and challenging problem. In order to address their interaction with the solar wind, sophisticated simulation techniques are necessary. Planetary bodies such as Mars, Titan and Venus are excellent subjects in comparing the interaction unmagnetized planetary atmospheres with the solar wind and provide insight into how atmospheres evolve differently throughout the solar system.
Venus does not have a magnetic field so the interaction of Venus' atmosphere with the solar wind (a constant energetic stream of particles coming off the Sun) is very different than Earth's. It is much more similar to the interaction of the solar wind with Mars, which also lacks a magnetic field but instead has remnant crustal fields on the surface extending up to almost 1000 km. Venus is 10 times more massive than Mars so the atmosphere is more gravitationally bound and less likely to escape. Like Mars, Venus was thought to have oceans of water on its surface at one point but it is now dry on the surface and has a very thick atmosphere that is extremely efficient at insulating the planet due to the runaway greenhouse effect from a mostly carbon dioxide atmosphere.
Solar System (690): Planetary Magnetospheres Laboratory
The Laboratory for Atmospheric and Space Physics (LASP)
The Department of Atmospheric, Oceanic and Space Sciences (AOSS)
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