A Mars orbiter circles the planet to observe it; missions such as Mars Odyssey and the Mars Reconnaissance Orbiter (MRO) also relay data from surface missions to Earth. Onboard autonomy, backup components and engineering margin have helped both spacecraft keep operating, though their reported aging challenges differ.
That long-running work matters because repeated observations let scientists track how Mars changes over time, while the relay link helps surface missions send their data home.
Two orbiters with a shared communications role
Mars Odyssey arrived at Mars on October 24, 2001. MRO arrived on March 10, 2006, NASA’s Jet Propulsion Laboratory (JPL) reported. Both orbiters relay data from surface robots to antennas in NASA’s Deep Space Network on Earth.
Their science roles differ. Mars Odyssey observes Martian ice, while MRO images changing surface features and helps assess landing sites and rover routes. MRO’s instruments have also supported research into Mars’s geology and possible seasonal liquid water.
How autonomy and backup systems help
Mars spacecraft may check in only once or twice a week, Wired reported in October 2026. Onboard systems therefore need to handle operations between contacts with Earth. Wired also reported that NASA duplicates vital spacecraft components, so a spare can support operations while engineers troubleshoot a failure.
MRO launched with more battery capacity and propellant than its mission strictly required, according to Wired. That extra capacity is an engineering margin: a reserve that can help a spacecraft continue operating when conditions or demands differ from expectations.
MRO’s star map and Odyssey’s propellant reserve
The two orbiters face different reported problems. In 2025, engineers sent MRO an updated star map after apparent shifts in stars’ positions affected its orientation references, Wired reported. The map helps the spacecraft use star observations to determine its orientation.
Mars Odyssey’s remaining propellant is uncertain, Wired reported, because the spacecraft has no fuel gauge. It uses propellant for small orientation adjustments, and engineers adapted its operations to use very small amounts.
What MRO’s long record revealed about Mars
JPL’s March 2016 retrospective reported that MRO had returned 264 terabits of science data by then, more than all other interplanetary missions combined. JPL also said all six of MRO’s science instruments remained productive more than seven years after the planned primary science phase ended.
The retrospective gave different coverage figures for three instruments: the HiRISE high-resolution camera had imaged about 2.4% of Mars; the Context Camera (CTX), which provides broader views, had imaged more than 95%; and the CRISM imaging spectrometer had covered nearly 98% in multiple visible-light and infrared wavelengths. These are figures from 2016.
A long record also lets scientists compare observations across several Martian years. JPL described MRO’s repeated observations as a way to track seasonal changes, including in research on possible seasonal liquid water.
