Every now and then, satellites in orbit around Earth have to do slight course-correction maneuvers, in order to avoid collisions with other satellites. And apparently the spacecraft around Mars have to deal with the same problem. NASA’s MAVEN spacecraft, which has been orbiting the Red Planet for the last two years, had to slightly alter its orbit this week so that it didn’t crash into the Martian moon Phobos.
MAVEN — or the Mars Atmosphere and VolatileEvolutioN spacecraft — inserted itself into Mars’ orbit on September 22nd, 2014, and since then the vehicle has been exploring the planet’s upper atmosphere and ionosphere. MAVEN’s orbit around Mars is a highly elliptical one, and NASA knows that the spacecraft crosses the orbits of other Martian orbiters and Phobos multiple times each year. But usually, these objects aren’t there when MAVEN crosses their paths.
But this week, NASA calculated that there was a “good chance” that MAVEN and Phobos would miss each other by about seven seconds next week. And since Phobos is a rock roughly 15 miles wide, it probably would have smacked into MAVEN, which is about the size of a small bus. So on Tuesday, NASA engineers prompted Maven to do an engine burn, boosting how fast MAVEN was moving by less than one mile per hour. Thanks to that small adjustment, NASA now estimates that next week MAVEN will miss Phobos by about two and a half minutes.
The move may mean MAVEN is safe to continue orbiting Mars, but Phobos is probably in for a rough ride over the next tens of millions of years. The small moon is slowly spiraling closer and closer to Mars, and in the next 20 to 40 million years, the planet may break apart Phobos. The debris of Phobos is expected to form a ring around Mars that will last for 1 million years.