The European Space Agency's (Esa) Mars Express spacecraft, which reached the Red Planet in 2003, has been granted a mission extension of one Martian year.
This extension is equivalent to about 23 months in Earth terms.
Mars Express has helped reveal a more complex view of the planet, including evidence for atmospheric methane, a frozen sea and geological activity.
But one of its science instruments may now have stopped working and deployment of its radar was delayed for a year.
The Marsis (Mars Advanced Radar for Subsurface and Ionosphere Sounding) was finally deployed in the middle of this year after fears that one or both of its 20m-long (65ft) booms might hit the spacecraft after opening out.
The mission extension should allow Marsis to restart its search for water reservoirs beneath the planet's surface in December.
Science instruments aboard the space probe have been building up global data on the composition and characteristics of the Martian surface and atmosphere.
This data has revealed that volcanic and glacial processes are much more recent than expected.
The Planetary Fourier Spectrometer (PFS) on Mars Express has detected methane gas in the atmosphere, at average levels of about 10 parts per billion. This finding has also been made by telescopes on Earth.
Methane is of great scientific significance because it has a finite lifetime in the atmosphere, so it must be replenished by some source on Mars.
Possible sources include volcanic activity, chemical processes on the surface, or - more controversially - microbial life.
The last hypothesis may even be supported by another finding by the spacecraft; that the distribution of water vapour and methane - both ingredients for life - overlap in some regions of the planet.
But further investigation of trace gases in the atmosphere may be hampered by the possible failure of the PFS.
Other notable discoveries include a frozen sea in the equatorial Elysium region.
The spacecraft was launched from Baikonur Cosmodrome in Kazakhstan aboard a Russian Soyuz rocket on 2 June 2003.
It was carrying the British-built Beagle 2 lander, which was designed to touch down on the Martian surface and test for past or present life.
The probe was due to establish contact with Earth once on the ground, but mission controllers failed to pick up its signal.
The decision to extend the Mars Express mission was taken on 19 September by Esa's Science Programme Committee.