It's an extraordinary possibility - the idea that living organisms are floating in the clouds of Planet Venus. But this is what astronomers are now considering after detecting a gas in the atmosphere they can't explain.
Nasa's Perseverance rover, due to launch to Mars this summer, will search an ancient crater lake for signs of past life. But if biology ever emerged on the Red Planet, how will scientists recognise it? Here, mission scientist Ken Williford explains what they're looking for.
Could "shadow life" be lurking in the deep ocean? Never mind Mars, alien life may be thriving right here on Earth, a major science conference has heard.
There is now even more evidence that life on Earth may have been seeded by material from asteroids or comets. Prior research has shown how amino acids - the building blocks of life - could form elsewhere in the cosmos.
US scientists have found further evidence that huge seas existed long ago on Mars. The 2,000 km-wide, 8km-deep Hellas basin is a giant impact crater - the largest such structure on Mars.
For decades, scientists have been sending robotic probes deep into the Solar System, revealing a diverse and dynamic array of worlds orbiting the Sun. Unmanned spacecraft have transformed understanding of our cosmic neighbourhood. But this avalanche of data has also thrown up many new questions.
It may not rank as the most compelling reason to curb greenhouse gases, but reducing our emissions might just save humanity from a pre-emptive alien attack, scientists claim.
Not many scientists are prepared to take tales of alien abduction seriously, but John Mack, a Harvard professor who was killed in a road accident in north London last year, did. Ten years on from a row which nearly lost him his job, hundreds of people who claim they were abducted still revere him.
The next generation of telescopes could reveal the presence of oceans on planets outside our Solar System. Detecting water on Earth-like planets offers the tantalising prospect they could sustain life.
Seti, the Search for Extraterrestrial Intelligence, has until now sought radio signals from worlds like Earth. But Seti astronomer Seth Shostak argues that the time between aliens developing radio technology and artificial intelligence (AI) would be short.
While searching deep space for extra-terrestrial signals, scientists at the Arecibo Observatory in Puerto Rico have stumbled across signals broadcast from Earth nearly half a century ago. Radio astronomer Dr.
The hunt for other intelligent civilisations has a new technique in its arsenal, but its first use has turned up no signs of alien broadcasts. Australian astronomers used "very long baseline interferometry" to examine Gliese 581, a star known to host planets in its "habitable zone".
The US government has formally denied that it has any knowledge of contact with extraterrestrial life. The announcement came as a response to submissions to the We The People website, which promises to address any petition that gains 5,000 signatories.
The powerful vision of the Hubble Telescope - which turns 20 this week - has expanded our cosmic horizons and brought into sharper focus a new set of mysteries about the universe that is our home. To those whose science is gleaned from the media, astronomy may seem to be on a roll. And it is.
The US Department of Defense has released three declassified videos of "unexplained aerial phenomena". The Pentagon said it wanted to "clear up any misconceptions by the public on whether or not the footage that has been circulating was real".
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