“During our mission we're hoping to see a handful of major storm events hit Mars and see what the reaction is,” Jakosky says. “If we are successful and are able to continue on in an extended mission, we have enough fuel to go from just after solar maximum to solar minimum and back up to solar maximum again. We may last as long as a decade.”
Changes in solar activity will be crucial to the measurements Maven is designed to make at the interface between atmosphere and space. If the thick Martian atmosphere disappeared into space, taking most of the planet's water with it, that is where the action would have been.
“The working model that we have is one in which, early in the history of the Solar System, the more intense extreme ultraviolet light from the Sun, the more intense solar wind, was able to strip off the atmosphere,” he says. “We think this happened very early. Prior to that, there was a thick atmosphere. Mars has a strong magnetic field that we see evidence today for it having been there 4 billion years ago. That magnetic field protected the planet; it stood off the solar wind, if you will, so it didn't hit the upper atmosphere and strip it off.”
When Mars lost its magnetic field, the theory goes, it lost that protection and with it the environment that may have made it habitable.
“Although we can't measure how it happened 4 billion years ago, we can examine the same processes as they're operating today, and learn enough to allow us to extrapolate back to the early history, and to determine the integrated loss over time,” says Jakosky.
Scout-class missions are managed from the beginning by the principal investigator, and Jakosky says he was fortunate in that he and his team “came as close as you can imagine to starting with a clean sheet—What do we want to learn? And what instruments can tell us what we need?”
In the end, the team selected eight instruments to study the upper atmosphere and ionosphere of Mars, and to conduct global remote sensing as the elliptical orbit moves toward and away from apogee.
The instrument suite consists of a Particles and Fields Package built by the Space Sciences Laboratory (SSL) at the University of California, Berkeley. Within the package are the Solar Wind Electron Analyzer (SWEA) to measure solar winds and electrons in the Martian ionosphere; the Solar Wind Ion Analyzer (SWIA), to measure solar wind and ion density and velocity in the planet's magnetosheath; the Suprathermal and Thermal Ion Composition (Static) instrument, which will measure ions in the atmosphere of Mars, including moderate energy escaping ions, and the Solar Energetic Particle (SEP) instrument to measure the impact of the solar wind on the planet's upper atmosphere.
The SWEA, SWIA, Static and SEP instruments all were provided by Berkeley's SSL. Also in the Particles and Fields Package are the Langmuir Probe and Waves (LPW) instrument supplied by LASP, which includes an extreme ultraviolet sensor. The LPW instrument will measure properties of the ionosphere, wave-heating in the upper atmosphere and extreme ultraviolet inputs into the atmosphere from the Sun. And Goddard Space Flight Center rounded out the package with a magnetometer, which will measure interplanetary solar wind and magnetic fields in the ionosphere.