The idea of humans one day colonizing Mars is a tantalizing one, but there are some obvious obstacles to our long-term residency on the red planet. Chief among them? The absence of water. Research has established that Mars used to have liquid water on its surface, but now it's a dry, dusty, inhospitable desert.

Today, NASA will launch a new mission — one that cost $671 million and has been in development for 10 years — to determine what happened to the water on Mars. The Curiosity rover has given us some insight into the conundrum, such as confirming that Mars used to host liquid water by spotting visible stream beds. Curiosity also established, via chemical analysis, that water still exists in Martian soil. It could be that some of the missing water has been absorbed into the soil or simply frozen. But scientists are intrigued by another possibility — water on Mars may have evaporated and been lost to space.

Water on Mars may have evaporated and been lost to space

The agency will now investigate that exact hypothesis with a new probe, called MAVEN, which will orbit around our red neighbor. MAVEN stands for Mars Atmosphere and Volatile EvolutioN, and as the name implies, MAVEN's mission is to characterize the Martian atmosphere. Researchers will use the data gathered by MAVEN to construct a history of the climate on Mars and paint a picture of how Mars lost its water.

Of course, this is no simple task. "It keeps you up at night," says Janet Luhmann, the deputy principal investigator of the MAVEN project. Luhmann is excited about how this mission will further our knowledge of Mars, but the exuberance at what she hopes MAVEN will reveal is tempered by the costs of bringing the project to fruition. "It's an investment financially. It's an investment in human energy and effort, and you want to make sure it succeeds, so it's stressful."

Weather permitting, MAVEN will launch today at 1:28PM ET from Cape Canaveral in Florida. So what does it take in order to peer into the distant past of the Martian atmosphere?

The mission

Mavenparts

The MAVEN mission is an exercise in collaboration, and the instruments onboard reflect that fact. The devices necessary for the venture have been provided by three different groups — the University of California, Berkeley; the University of Colorado; and NASA's Goddard Space Flight Center. And each of these groups will use data provided by the equipment to glean insights into long-lost Martian water.

An Atlas V rocket will blast the nearly 3-ton MAVEN probe into space. Once MAVEN's solar arrays are fully extended, the craft will be as long as a school bus. When it arrives on Mars, it won't travel in a traditional circular orbit that would keep MAVEN at a constant distance from the planet. Instead, MAVEN will orbit in an elliptical path that will alternately bring it close to and far from the planet. At its furthest point from Mars, MAVEN will be 3,900 miles away in order to better measure the effects of the sun. MAVEN's elliptical orbit will also bring it within 93 miles of the planet to characterize the upper atmosphere. In addition to these regular close sweeps, MAVEN will perform five "deep dives" where it will dip even further — 78 miles from the surface — to profile the atmosphere at a lower altitude.

A holistic picture of the Martian atmosphere

The probe contains a suite of instruments that will give researchers a holistic picture of the Martian atmosphere, how it changes, and the role the sun has played in removing the planet's atmosphere: scientists think there's an important, but complex, relationship between the loss of water on Mars and other atmospheric gases and solar activity. MAVEN's instruments will characterize the gases and ions that are leaving the planet, and determine the extent to which these losses are due to energetic particles in solar wind — essentially a spew of material emitted by the sun — kicking the gases out of the atmosphere.

The Earth is largely protected from these events due to strong magnetic fields from its iron core, but Mars has a much weaker magnetic field, making the planet more susceptible to the effects of solar storms. Researchers speculate that when the Martian atmosphere is hit with solar wind, some of its gases are removed. That drier atmosphere then creates a driving force for water to evaporate. If scientists can track the evolution of the atmosphere, and corresponding solar activity, over the yearlong mission, they might be able to project the state of the atmosphere back in time to test the hypothesis as an explanation for Mars' loss of water.

That tracking remains a ways off: it will take about 10 months for the probe to arrive at the red planet, and researchers hope to start gathering useful information around November of 2014. But the mission could have taken much longer to get moving: the recent US government shutdown threatened MAVEN's launch window, meaning NASA would have had to wait for the planets to align, so to speak, to select another departure date.

The payoff

Mars_before_and_after

Mars today, shown at left, is dry and inhospitable. But as indicated in the right, the planet may once have been a much more watery place.

The MAVEN mission is expected to change how we think of and interact with Mars, both in the near and long term. Having another satellite orbiting the planet will immediately aid other Mars-oriented research. MAVEN contains a relay, for instance, that will increase the data-transfer capabilities of missions like Curiosity and the InSight lander, expected to launch in 2016 with plans to probe for seismic activity.

How to one day colonize the Red Planet

This research will also aid investigators as they continue to study exoplanets. Teams have been scouting for planets that orbit in the not-too-hot, not-too-cold region around our sun called the habitable zone, in hopes of finding planets that may harbor life. However, while there are three planets around our sun considered to be in this zone, only Earth — and not Venus or Mars — seems to harbor life. Learning more from Mars will help scientists understand why, and offer them new clues as they hunt for life across the universe.

MAVEN might also help us figure out how to one day colonize the Red Planet. When asked about a far-off future where we might terraform the thin Martian atmosphere to be breathable, Luhmann speculates that Mars' atmospheric history will make that impractical. Instead, humans may live in biospheres and produce a local atmosphere within them. "I think a limited, controlled, enclosed environment would be the way you would have to go," Luhmann says. "Doing the whole planet is science fiction."

"Part of the treasure trove of the science of humankind."

For those keen to track MAVEN's progress, NASA will be posting to Twitter, allowing anyone to follow the project as a spectator. And scientists are hoping to see more active citizen involvement too: the data gathered by MAVEN will be released to the public through their Planetary Data System portal. "We're going to make unique measurements and have a unique dataset that will be part of the treasure trove of the science of humankind," Luhmann says. "The rewards are potentially huge. The rewards are ultimately that you're going to increase human understanding [of the universe] forever."