ExoMars - a joint European and Russian mission - is now nearing the red planet and will soon jettison a lander towards the Martian surface.
It's hoped the mission will solve why there is methane on the red planet and also test technologies for future Mars missions.
On October 16, just three days before arriving on Mars, the TGO - 'Trace Gas Orbiter' - will release its lander, called Schiaparelli. It's named after Giovanni Schiaparelli, an Italian astronomer who mapped the red planet's surface features during the 19th century.
"We separate not too early so that the accuracy of landing is good, but also not too late so that we have time then to re-orientate the TGO and actually raise its altitude and not crash on Mars," explains flight operations director, Michel Denis.
"It is on a collision course up to the moment of separation so that it can bring Schiaparelli to the ground, to the centre, hopefully, of a landing ellipse."
The landing site is close to Mars' equator and measures around 100km in length and 15km in width. It's in a relatively smooth and flat region that's well studied by scientists.
Schiaparelli will use a heat shield, parachute and propulsion systems to slow its descent towards the rocky Martian surface. This is to test technology that will be used for ESA's ExoMars rover mission in 2020. It's also to test the landing site's environment.
Descent will take around six minutes and it's expected to land on Mars on October 19.
Above, the TGO will slowly fall into Mars' orbit in order to observe its atmosphere using an array of scientific instruments. It will search for evidence of gasses such as methane.
In December 2014, NASA's Mars rover, Curiosity, detected spikes of methane in the planet's atmosphere. That suggests something is producing or venting the scientifically tantalising gas.
Most of Earth's atmospheric methane comes from animal and plant life, and the environment itself. So the Martian methane raises the question of past or present microbial life. Or the gas elevations could come from geological sources, comet impacts or something else entirely.
In order to enter orbit, the TGO will have to gradually lower its orbit using a brand new technology developed by ESA, called 'aerobraking'.
"With ExoMars, ESA is going to use for the first time a method called aero-braking for a spacecraft in orbit around Mars to decrease the orbit by letting it fly through the atmosphere and using the atmospheric density to slow it down instead of using fuel for the engines," says ExoMars spacecraft operations engineer Johannes Bauer.
It's expected to begin its science mission by the end of 2017 following a year of complex manoeuvres which lower it to a 400km circular orbit.
TGO will also be used to relay communications with Earth for current and future Mars missions. That means it will be used to relay messages from the ExoMars rover in 2020.
It's been around seven months since blast off in Kazakhstan. Now, the next stage is looming for ESA's latest mission to Mars.
Europe's Beagle 2 probe disappeared during the landing process in 2003, a setback which ESA is keen to avoid this time.
ExoMars is a joint mission between the European Space Agency and Russia's Roscosmos space agency.
APTN / Newshub.
