Nearby planets that look unusually alike could be a sign of spacefaring alien life that has travelled between stars, researchers have suggested.
Astronomers searching for extraterrestrial life tend to look for specific signals, either in the form of 鈥渂iosignatures鈥� 鈥� molecules that are only produced by biological processes 鈥� or 鈥渢echnosignatures鈥�, abnormal patterns of light that may have been produced by technologies.
Both of these rely on assumptions about how life might function on another world, which is largely based on our knowledge of life on Earth. However, this approach risks missing signals from alien life forms that might be very different to us.
Advertisement
at the Sony Computer Science Laboratories in Japan and at the Tokyo Institute of Technology have proposed a new biosignature that doesn鈥檛 rely on any specific molecule, but instead looks for similarities between planets in neighbouring star systems that life may have colonised. 鈥淲e鈥檙e trying to make very few assumptions about what this life looks like because we know nothing about what life, in general, could look like,鈥� says Smith.
Sinapayen and Smith start by assuming that life can spread between planets, either intentionally or by accident 鈥� an idea known as panspermia. They also assume that it will somehow change the environment of the planets that it lands on, called terraformation.
The pair simulated a universe containing 1000 planets, each around a different star, with one planet that was sending out life in all directions. When life reached another planet, it would terraform it.
They then ran the simulation forwards in time to see which statistical patterns would appear between nearby groups of planets, irrespective of the kind of signal they were giving off, like a specific molecule or planetary temperature. Based on this, they came up with a test to determine whether signals from a group of planets might contain life and a method to identify which planet in the group the life may have originated from.
The study looks at an interesting combination of two possible ways that alien life may function, in panspermia and terraformation, says at the University of Warwick, UK. However, these mechanisms might not be possible, he says.
Even if terraformation was possible, it would be difficult to rule out the possibility that nearby planets had similar compositions for other, non-biological reasons, he says. 鈥淭here鈥檚 a couple of things there that I think would stop this being a 鈥榦ne and done, we鈥檝e definitely found life if we see this鈥� kind of output,鈥� says Armstrong.
We will also need better telescopes to reliably start detecting molecules in exoplanet atmospheres, which would be needed for this kind of similarity analysis, says Armstrong. 鈥淲hen we get to that stage, you鈥檒l be able to just look at lots of planets to try and find certain chemicals, so there鈥檒l be a lot of angles to explore there in terms of habitability.鈥�
arXiv
