Technicians work on the MAVEN spacecraft at NASA's Kennedy Space Center in Florida before its 2013 launch.
Photo: NASA/Kim Shiflett.
But NASA's two other Mars orbiters have been in space for more than 20 years. The eldest of the two named Mars Odysseyhas been on Mars since 2001 and will soon run out of fuel, possibly within the next couple of years. NASA Mars Reconnaissance Orbiterlaunched in 2005, it is quite healthy for its age and has enough fuel to last until the 2030s. MRO is also important to NASA because it has the best camera on Mars, allowing it to map landing sites for future missions.
Two European spacecraft, Mars Express and ExoMars Trace Gas Orbiter, are equipped with radios to transmit data between mission controllers and NASA landers on the surface of Mars. Mars Express, now 22 years old, suffers from the same aging problems as Mars Odyssey and MRO. The ExoMars Trace Gas orbiter is newer, arriving on Mars in 2016, but is also nearing the end of its lifespan.
China and the United Arab Emirates also have orbiters circling Mars, but neither spacecraft is equipped to act as a communications relay.
NASA's Mars rovers Curiosity and Perseverance have the ability to communicate directly with Earth, but the orbital relay network can support significantly higher data throughput. Without satellites overhead, much of the scientific data and many of the impressive images collected by NASA's Mars rovers may never make it off the planet.
MAVEN's unique orbit, extending 2,800 miles (4,500 kilometers) above Mars, has some advantages for data transmission. In this orbit, MAVEN can transmit science data from rovers to the surface for up to 30 minutes at a time, exceeding the relay periods available through NASA's low-altitude orbiters. This allows MAVEN to support the largest data volumes of any relay option.
