Are aliens hiding in plain sight?

Several missions this year are seeking out life on the red planet. But would we recognise extraterrestrials if we found them?

In July, three unmanned missions blasted off to Mars - from China (Tianwen-1), the US (Nasa's Mars 2020 Perseverance Rover) and the United Arab Emirates (Hope). The Chinese and American missions have lander craft that will seek signs of current or past life on Mars. Nasa is also planning to send its Europa Clipper probe to survey Jupiter's moon Europa, and the robotic lander Dragonfly to Saturn's moon Titan. Both moons are widely thought to be promising hunting grounds for life in our solar system - as are the underground oceans of Saturn's icy moon Enceladus.

Meanwhile, we can now glimpse the chemical makeup of atmospheres of planets that orbit other stars (exoplanets), of which more than 4,000 are now known. Some hope these studies might disclose possible signatures of life.