MAVEN Spacecraft Makes Evasive Maneuver to Avoid Impact With Mars' Moon Phobos

Orbital correction needed to avert collision in early March.

Artist's illustration of MAVEN in orbit around Mars. Image by NASA

Artist's illustration of MAVEN in orbit around Mars. Image by NASA

Mars is a busy place these days, with multiple rovers and orbiters exploring the planet. Out of the several spacecraft currently in orbit, NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) is a fairly recent addition, having been at Mars for just over two years now. Usually, things are pretty routine, but this week the spacecraft had to make an unplanned evasive maneuver - to avoid a collision with one of Mars' two small moons, Phobos!

MAVEN is in an elliptical orbit around Mars which at times takes it across the orbits of Phobos and some other orbiters. If the spacecraft were to arrive at the same spot as Phobos at the same time, they could easily collide. In order to prevent this, a small correction must be made to MAVEN's orbit in advance. On Tuesday, Feb. 28, such an adjustment was made, which boosted the spacecraft's velocity by 0.4 meters per second (less than 1 mile per hour). This was done about one week before the projected collision could occur, which means that MAVEN should miss Phobos in its orbit by about 2.5 minutes. Previously it was estimated that MAVEN and Phobos had a good chance of colliding on March 6; they would have arrived at the orbit crossing point within only 7 seconds of each other - a rather close call, at best.

As MAVEN Principal Investigator Bruce Jakosky explained, "Kudos to the JPL navigation and tracking teams for watching out for possible collisions every day of the year, and to the MAVEN spacecraft team for carrying out the maneuver flawlessly."

Phobos

Phobos, the largest of Mars' two tiny moons. Photo by NASA/JPL-Caltech

Phobos, the largest of Mars' two tiny moons. Photo by NASA/JPL-Caltech

Phobos may be a tiny moon but a collision would still be catastrophic of course for MAVEN. This was the first time that such a maneuver correction had to be made for the spacecraft; the orbits of both MAVEN and Phobos are well-known and constantly monitored with just such scenarios in mind.

MAVEN has been busy studying Mars' upper atmosphere, ionosphere and interactions with the Sun and solar wind. The spacecraft has observed how water vapor escapes from the upper atmosphere into space.

“MAVEN is giving us unprecedented detail about hydrogen escape from the upper atmosphere of Mars, and this is crucial for helping us figure out the total amount of water lost over billions of years,” said Ali Rahmati, a MAVEN team member at the University of California.

The findings help scientists to understand how Mars changed from a once much wetter and more hospitable world billions of years ago to the dry desert planet we see today. Most of Mars' former water is thought to have escaped to space, while the rest is now mostly frozen at the poles and underground.

Auroras on Mars

An aurora in Mars' northern hemisphere as seen in ultraviolet by MAVEN in December 2014. Image by University of Colorado

An aurora in Mars' northern hemisphere as seen in ultraviolet by MAVEN in December 2014. Image by University of Colorado

“MAVEN’s findings reveal what is happening in Mars’ atmosphere now, but over time this type of loss contributed to the global change from a wetter environment to the dry planet we see today,” said Rahmati.

“Taken together, the MAVEN results tell us that loss of gas from the atmosphere to space has been the major force behind the climate having changed from a warm, wet environment to the cold, dry one that we see today,” said Bruce Jakosky, MAVEN principal investigator, from the University of Colorado in Boulder.

MAVEN has also mapped auroras in Mars' northern hemisphere, using its Imaging Ultraviolet Spectrograph (IUVS). In December 2014, an extensive aurora was detected in all observations during a five-day period.

"It really is amazing," said Nick Schneider who leads MAVEN's Imaging Ultraviolet Spectrograph (IUVS) instrument team at the University of Colorado. "Auroras on Mars appear to be more wide ranging than we ever imagined."

The MAVEN mission has helped to revolutionize scientists' understanding of Mars ancient history; as long as it avoids any future collisions or other mishaps, it should still continue to do so for a long time.

More information about the MAVEN mission is available here.

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MAVEN Spacecraft Makes Evasive Maneuver to Avoid Impact With Mars' Moon Phobos
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