It's been only three weeks since NASA's MAVEN spacecraft entered into orbit around Mars and already the mission sending back science. In a first step towards MAVEN's main goal of unlocking Mars' climate history, the spacecraft's Imaging Ultraviolet Spectrograph has taken a series of four false-color images showing the distribution of hydrogen and oxygen in Mars' atmosphere.
Mars' scant atmosphere contains both hydrogen and oxygen, two gases that are produced on the red planet when water and carbon-dioxide break down. Both are held to the planet by Mars' gravity, but because Mars' gravity is only about one-sixth of what we feel on Earth, the gases can escape into space more easily. As these false color images show, oxygen, the heavier of the two gases, sits fairly low in the atmosphere while the much lighter hydrogen gas expands as it rises to higher altitudes where it can escape. The image shows it fanning out around the planet out of frame.
Why and how Mars' atmospheric gases escaped is what MAVEN is after, and one of the leading candidates for atmospheric loss is weather. We have a magnetic field enveloping the Earth that protects us from the brunt of the Sun's destructive forces, things like solar wind and radiation. Mars doesn't have a strong magnetic field to protect it from space weather; the planet has a spotty array of magnetic fields that protect some areas more than others but is overall not a good defense.
Millions of years of solar storms and solar winds ripping by the planet are thought to have stripped away a significant amount of the Martian atmosphere, leaving us the desiccated, barren world we know today.
The Imaging Ultraviolet Spectrograph is part of MAVEN's Remote Sensing Package designed to remotely measure the global characteristics of Mars' upper-atmosphere and ionosphere. Specifically, IUVS is looking at the atmosphere's vertical profile to understand its composition, structure, spatial distribution, variability, and also indirectly characterize the lower atmosphere.
It's also the instrument that can see solar stripping in action. The ideal scenario would be to observe Mars in the aftermath of a coronal mass ejection. A CME is a pretty significant event wherein a billion-ton cloud of ionized gas is blasted away from the Sun in the wake of a solar flare. On Earth, thanks to our magnetic field, CMEs rattle the planet and cause the Northern Lights. Sometimes a really powerful CME can cause blackouts, but that's about as bad as it gets. On Mars, which lacks a magnetic field's protective envelope, the effects are untempered. A gust of solar wind and a CME strike could strip material right out of the atmosphere.
Or, the opposite could happen. Wrapped up in MAVEN's overall atmospheric mission is to understand what Principle Investigator Bruce Jakosky calls solar forcing. "On the one hand, a CME might strip the outermost layers of the atmosphere," he explains. "On the other, it might also energize the atmosphere below and repopulate the extended atmosphere with a lot of new material." Whatever the case, MAVEN will see something.
The data from IUVS will ultimately be paired with data form the other spacecraft instruments, the Neutral Gas and Ion Spectrometer and the Particles and Fields Package. If we're getting this kind of data after three weeks—and these images were actually returned only eight hours after MAVEN entered Martian orbit on September 21—imagine what we'll get in the months to come. This mission is going to be awesome.