In the UK, they were phased out as front-line bombers by the end of 1961, but about 50 were kept on for training, photographic reconnaissance, communications and jamming enemy radar.

BBC: NEWS | UK | Fact file: Canberra PR9

Using a ground-piercing radar sensor aboard the Mars Reconnaissance Orbiter, a team of scientists created 3-D maps of an equatorial region known as Elysium Planitia and the channels that run underneath the plains.

NPR: Radar Reveals Apparent Buried Channels On Mars

Data from the Sharad (SHAllow RADar) instrument (on Mars Reconnaissance Orbiter), document that some of these glacial-like features, which you find at Mars' mid-latitudes, have a significant volume of ice left below a surface of rock debris.

BBC: Q&A: Liquid water on Mars

According to Mr Clark, earlier, unmanned Shenzhou missions have carried photo-reconnaissance equipment and probes that could spy on military-radar transmissions.

ECONOMIST: China in space