A small robot could make history by becoming the first European spacecraft to survive a landing on Mars later.
Scientists will be hoping the Schiaparelli probe successfully flies itself through the Martian atmosphere and lands on Meridiani Planum - an area near the planet's equator rich in haematite.
On Earth, the mineral almost always forms in a watery environment.
The mission, conducted by the European Space Agency (Esa), will test out a landing system for future missions to the Red Planet - including the ExoMars Rover mission in 2020.
The ExoMars Rover will drill into the soil of Mars and look for definitive signs of past or present life.
It is expected the Schiaparelli probe will land at 3.48pm UK time.
The only previous Esa spacecraft to attempt a landing on the planet was British-build Beagle 2 on Christmas Day 2003.
After separating from the Mars Express orbiter that carried it, Beagle 2 was never heard from again.
However in 2015 scientists discovered the Beagle had landed, but its solar panels had failed to deploy.
Mission controllers hope Schiaparelli - part of an ambitious joint European and Russian space effort - will fare better and take photographs of the approaching terrain.
Schiaparelli was taken to Mars on the ExoMars Trace Gas Orbiter (TGO) spacecraft, and has crossed a distance of 500 million km on a seven-month journey from Earth.