It sounds like science fiction, but the theory of panspermia, in which life can naturally transfer between planets, is considered a serious hypothesis by planetary scientists. The suggestion that life did not originate on Earth but came from elsewhere in the universe (for instance, Mars), is one possible variant of panspermia. Planets and moons were heavily bombarded by meteorites when the Solar System was young, throwing lots of material back into space. Meteorites made of Mars rock are occasionally found on Earth to this day, so it is quite plausible that simple life forms like yeasts or bacteria could have been carried on them.
Yet serious questions remain for supporters of this theory. Would even the hardiest life forms be able to survive an impact which ejects the rock into space? Could they live through the freezing temperatures and deadly radiation of space? And could they enter the atmosphere and hit the surface of the earth without being killed?
New research presented at the European Planetary Science Congress at UCL aims to answer the final question, of whether entry and impact is survivable for simple organisms. Using frozen samples of Nannochloropsis oculata, a type of single-celled ocean-dwelling algae, Dina Pasini (University of Kent) set out to test the conditions which early life would have had to survive if it did indeed travel through space.
Using a two-stage light gas gun, which can accelerate objects up to very high speeds, Pasini fired frozen pellets of Nannochloropsis into water, and tested the samples to see if any had survived.
“As you might expect, increasing the speed of impact does increase the proportion of algae that die,” Pasini explains, “but even at 6.93 kilometres per second, a small proportion survived. This sort of impact velocity would be what you would expect if a meteorite hit a planet similar to the Earth.”
As well as surviving freezing and impacts, like those experienced when rocks are ejected from planets or hit them, there are good reasons to think that the other problems faced by panspermia are not insurmountable either. Ice and rocks can provide protection against radiation, especially if the organism is deeply embedded inside. What is more, heating caused by entry into the atmosphere is unlikely to heat anything more than a thin layer around the outside of rocks, forming what is known as a ‘fusion crust’.
This research suggests that panspermia, while certainly not proven, is not impossible either.
“Our research raises several questions,” Pasini says. “If we find life on another planet, will it be truly alien or will it be related to us? And if so, did it spawn us or did we spawn it? We cannot answer these questions just now, but the questions are not as farfetched as one might assume.”
Asteroid impacting Earth's oceans. Credit: NASA/Don Davis
NOTES FOR EDITORS
About the European Planetary Science Congress (EPSC)
EPSC is the major European meeting on planetary science. EPSC 2013 is taking place at University College London (UCL) from Sunday 8 September to Friday 13 September 2013. It is the first time that the Congress has been held in the UK. The 2013 programme includes around 75 sessions and workshops. Details of the Congress and a full schedule of EPSC 2013 scientific sessions and events can be found at the official website: http://www.epsc2013.eu/
EPSC 2013 is organised by Europlanet, UCL and Copernicus Meetings and the event is sponsored by the UK Space Agency, UCL, Astrium and the Science and Technology Facilities Council.
To celebrate EPSC coming to London, a ‘Festival of the Planets’ has been organised across the Capital in collaboration with partners including the Baker Street Irregular Astronomers, the Bloomsbury Theatre, the British Astronomical Association, the British Interplanetary Society, the Natural History Museum, the Open University, Queen Mary University of London, the Royal Astronomical Society, Royal Museums Greenwich and University College London. More information about the events can be found at: http://www.europlanet-eu.org/epsc2013/outreach-activities
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About Europlanet Europlanet is a network of planetary scientists, whose aim is to bring together the disparate European community so that Europe can play a leading role in space exploration. Europlanet’s activities complement the mission activities of the European Space Agency through field work at planetary-analogue terrains on Earth, laboratory measurements, computer modelling and observations from ground-based telescopes. Founded in 2002 and funded by the European Commission from 2005-2012, Europlanet has evolved into a community-based organisation that will carry on this work and plan for future missions and mission support.
About UCL (University College London)
Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender and the first to provide systematic teaching of law, architecture and medicine.
UCL is among the world's top universities, as reflected by its performance in a range of international rankings and tables. According to the Thomson Scientific Citation Index, UCL is the second most highly cited European university and the 15th most highly cited in the world.
UCL has nearly 27,000 students from 150 countries and more than 9,000 employees, of whom one third are from outside the UK. The university is based in Bloomsbury in the heart of London, but also has two international campuses – UCL Australia and UCL Qatar. Its annual income is more than £800 million. www.ucl.ac.uk | Follow UCL on Twitter @uclnews | Watch our YouTube channel YouTube.com/UCLTV