ESA 's next mission , BepiColombo , will explore the planet closest to the Sun , Mercury . The probe will launch in 2016 and reach Mercury in 2020 . It will endure temperatures of 350 degrees Celsius and observe Mercury from orbit . Nevertheless , ESA feels that there is enough mystery about Mercury to warrant a third mission . The data will be used , among other things , to test Einstein 's theory of relativity .
ESA 's next mission , BepiColombo , will explore the planet closest to the Sun , Mercury . The probe will launch in 2016 and reach Mercury in 2020 . It will endure temperatures of 350 degrees Celsius and observe Mercury from orbit . The data will be used , among other things , to test Einstein 's theory of relativity .