Home stretch! This Sunday, after a 10-month journey across the inner solar system, NASA’s MAVEN spacecraft will finally reach the Red Planet. The orbiter could provide the elusive answer to a simple question: If Mars once had enough atmosphere to allow for liquid water on its surface, then where did it all go?
The spacecraft is now flying solo until it enters Martian orbit. “MAVEN orbit insertion sequence has been activated on the [spacecraft],” officials tweeted Thursday. “No additional ground intervention is needed.”
The spacecraft, the first mission to examine the planet’s upper atmosphere, was 218 million kilometers away from Earth on Wednesday and a mere 1.2 million kilometers from Mars. Given that it was zooming through space at a speed of 81,000 kilometers per hour, it has probably significantly closed the distance to its target.
“We’re really excited about the science we’re going to do,” lead scientist Bruce Jakosky, a planetary scientist at the University of Colorado, Boulder, said in a briefing Wednesday. “It’s been a lot of effort from hundreds of people to get here.”
Just weeks after the Mars Atmosphere and Volatile EvolutioN spacecraft enters orbit this Sunday, it will receive an awesome housewarming gift: a freshly discovered comet that will buzz the atmosphere and provide a sort of natural experiment. As comet Siding Spring comes within 130,000 kilometers of Mars, the comet (known formally as C/2013 A1) will potentially allow scientists to observe its effects on the atmosphere.
“I’m told that the odds of having an approach that close to Mars are about one in a million years,” Jakosky said. “So it’s really luck that we get the opportunity here.”
Earth sits in the habitable zone between Venus and Mars, sandwiched by two alternate fates. Venus has too much atmosphere, while Mars has too little. But researchers think that, early in Mars’ history, the planet had a thick atmosphere that could have supported clear lakes and puffy clouds. A thick-enough atmosphere is key, because liquid water will quickly boil away or freeze solid without it. But at some point, that atmosphere began to disappear – and now, billions of years later, the Red Planet’s atmosphere is less than 1% that of Earth’s.
If water fled the Red Planet’s surface, it had two escape routes: deep into the ground, or up into space. MAVEN, launched in November, will investigate that second escape route. The mission will study the top layers of Martian atmosphere – that interface between the thicker atmosphere below and the harsh vacuum of space above – to see how its protective bubble of gas was eventually whittled away.
By studying the atmospheric processes today, they hope to work backward to understand exactly what the Martian environment once looked like, and how it was lost.
The primary mission is set for one year — though Guy Beutelschies, Lockheed Martin’s MAVEN program manager, said there’s enough fuel to last several more. Later in its life, the orbiter will serve as one of the relay stations for the Mars rover Curiosity, catching its data from the planet’s surface and relaying it home to Earth.
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