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This artist's rendering shows NASA's MAVEN spacecraft in orbit around Mars, with a whimsical depiction of its home planet in the background. | Source: NASA/GSFC
Another corpse just appeared in the Martian graveyard.
On Wednesday (June 3), NASA officially announced the retirement of its MAVEN orbiter, bringing to a close a highly successful mission to study the Red Planet's atmosphere that lasted nearly twelve years.
The MAVEN team hadn't planned for this outcome; the orbiter suddenly shut down last December and remained silent despite repeated attempts to contact it. But MAVEN's fate would have ultimately been much the same, even if its operators had managed to shut it down in a controlled manner.
«"The official plan for disposing of the spacecraft at the end of its mission was to leave it in this official orbit, where it would remain for 50 to 100 years before entering the Martian atmosphere," MAVEN project manager Mike Moreau of NASA's Goddard Space Flight Center in Greenbelt, Maryland, said at a press conference Wednesday.
«"Thus, the spacecraft is in a configuration, in orbit, very similar to what it would have been if the mission had ended normally," he added.
This is precisely what happens to defunct Mars orbiters: they typically continue orbiting for half a century or more, until the planet's thin atmosphere pulls them down and incinerates them. Or they can meet their end much sooner if they're unlucky enough to collide with one of their fellow Mars moons, Phobos or Deimos. (Indeed, in February 2017, MAVEN had to maneuver to avoid a potential collision with Phobos.)
Given the long history of Mars exploration, some of these probes may have already been delivered to Earth. Here's a brief overview of the orbiter missions that have successfully arrived on the Red Planet to date:
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«Mariner 9 (NASA; arrived November 1971)
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Mars-2 (USSR; November 1971)
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Mars 3 (USSR; December 1971)
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Mars 5 (USSR; February 1976)
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Viking 1 (NASA; June 1976)
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«Viking 2 (NASA; August 1976)
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Phobos 2 (USSR; January 1989)
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Mars Global Surveyor spacecraft (NASA; September 1997)
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Mars Odyssey (NASA; October 2001)
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Mars Express (European Space Agency; December 2003);
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Mars Reconnaissance Orbiter, or MRO (NASA; March 2006)
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Mars Orbiter Mission (India; September 2014)
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MAVEN (NASA; September 2014)
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ExoMars Trace Gas Orbiter, or TGO (ESA; October 2016)
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United Arab Emirates Mars Mission, or Hope (UAE; February 2021)
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Tianwen 1 (China; February 2021)
Today, only Mars Odyssey, Mars Express, MRO, TGO, Hope, and Tianwen 1 remain operational, meaning there are up to a dozen bodies in the orbital graveyard. (Tracking defunct spacecraft in Mars orbit is difficult, so we generally don't know which ones are still in space.)
There's a graveyard on the surface of Mars, too. Among the many robots buried beneath the wind-blown red earth are NASA's Spirit and Opportunity rovers, the Ingenuity helicopter, the Pathfinder lander (which Mark Watney discovers and uses in the book and film The Martian), and the Zhurong rover, which was part of China's Tianwen 1 mission.
Today, only two Mars rovers remain operational: Curiosity and Perseverance, which landed in August 2012 and February 2021, respectively.
But let's finish with a shout-out to MAVEN (which stands for "Mars Atmosphere and Volatile Evolution"). The data it collected helped scientists better understand Mars's dramatic transition from a relatively warm and humid world to the frigid desert we know today.
This change occurred because Mars lost most of its once-thick atmosphere. (The planet's air density is now only 1% of that on Earth at sea level.) Thanks to MAVEN, we know that this loss was caused by the solar wind and occurred between 4.2 and 3.7 billion years ago—around the time life began on Earth.