A meeting of astrobiologists results in a target list of developments needed in the next two decades. Lauren Fuge reports.
Move over Mars rovers, new technologies to detect alien life are on the horizon.
A group of scientists from around the world, led by astrochemistry expert Chaitanya Giri from the Tokyo Institute of Technology in Japan, have put their heads together to plan the next 20 years’ worth of life-detection technologies. The study is currently awaiting peer review, but is freely available on the pre-print site, ArXiv.
For decades, astrobiologists have scoured the skies and the sands of other planets for hints of extraterrestrial life. Not only are these researchers trying to find ET, but they’re also aiming to learn about the origin and evolution of life on Earth, the chemical composition of organic extraterrestrial objects, what makes a planet or satellite habitable, and more.
But the answers to such questions are preceded by long years of planning, development, problem-solving and strategising.
Late in 2017, 20 scientists from Japan, India, France, Germany and the USA – each with a special area of expertise – came together at a workshop run by the Earth-Life Science Institute (ELSI) at Giri’s Tokyo campus. There, they discussed the current progress and enticing possibilities of life-detection technologies.
In particular, the boffins debated which ones should be a priority for research and development for missions within the local solar system – in other words, which instruments will be most feasible to out onto a space probe and send off to Mars or Enceladus during the next couple of decades.
Of course, the planets and moons in the solar system are an extremely limited sample of the number of potentially habitable worlds in the universe, but understanding our own backyard will be key in interpreting data from far-flung exoplanets.
So, according to these astrobiology experts, what’s the future plan for alien detection?
The first step of any space mission is to study the planet or satellite from afar to determine whether it is habitable. Luckily, an array of next-generation telescopes is currently being built, from the ultra-sensitive James Webb Space Telescope, slated for launch in 2021, to the gargantuan Extremely Large Telescope in Chile, which will turn its 39-metre eye to the sky in 2024. The authors point out that observatories such as these will vastly expand our theoretical knowledge of planet habitability.
Just because a world is deemed habitable doesn’t mean life will be found all over it, though. It may exist only in limited geographical niches. To reach these inaccessible sites, the paper argues that we will require “agile robotic probes that are robust, able to seamlessly communicate with orbiters and deep space communications networks, be operationally semi-autonomous, have high-performance energy supplies, and are sterilisable to avoid forward contamination”.
But according to Elizabeth Tasker, associate professor at the Japan Aerospace Exploration Agency (JAXA), who was not involved in the study, getting there is only half the struggle.
“In fact, it’s the most tractable half because we can picture the problems we will face,” she says.
The second, more pressing issue is how to recognise life unlike anything we know on Earth.
As Tasker explains: “We only have Earth life to compare to and this is the result of huge evolutionary history on a planet whose complex past is unlikely to be replicated closely. That’s a lot of baggage to separate out.”
According to the paper, the way forward is to equip missions with a suite of life-detection instruments that don’t look for life as we know it, but are instead able to identify the kinds of features that make organisms function.
The authors outline a huge variety of exciting technologies that could be used for this purpose, including spectroscopy techniques (to analyse potential biological materials), quantum tunnelling (to find DNA, RNA, peptides, and other small molecules), and fluorescence microscopy (to identify the presence of cell membranes).
They also nominate different forms of gas chromatography (to spot amino acids and sugars formed by living organisms, plus checking to see if molecules are “homochiral” (a suspected biosignature) using microfluidic devices and microscopes.
High-resolution, miniaturised mass spectrometers would also be helpful, characterising biopolymers, which are created by living organisms, and measuring the elemental composition of objects to aid isotopic dating.
Giri and colleagues also stress that exciting developments in machine learning, artificial intelligence, and pattern recognition will be useful in determining whether chemical samples are biological in origin.
Interestingly, researchers are also developing technologies that may allow the detection of life in more unconventional places. On Earth, for example, cryotubes were recently used to discover several new species of bacteria in the upper atmosphere.
The study notes that with the use of these burgeoning technologies, missions will likely generate huge amounts of data and require upgrades to the existing current deep space communication network.
The scientists also discuss how certain technologies – such as high-powered synchrotron radiation and magnetic field facilities – are not yet compact enough to fly to other planets, and so samples must continue to be brought back for analysis.
Several sample-and-return missions are currently underway, including JAXA’s Martian Moons exploration mission to Phobos, Hayabusa-2 to asteroid Ryugu, and NASA’s OSIRIS-rex to asteroid Bennu. What we learn from handling the organic-rich extraterrestrial materials brought back from these trips will be invaluable.
The predictions and recommendations put forward by Giri and colleagues are the first steps in getting these technologies discussed in panel reviews, included in decadal surveys, and eventually funded.
They complement several similar efforts, including a report prepared by US National Academies of Science, Engineering and Medicine (NASEM), calling for an expansion of the range of possible ET indicators, and a US-led exploration of how the next generation of radio telescopes will be utilised by SETI.
Perhaps most importantly, these papers all highlight the need for collaborative work between scientists across disciplines.
“A successful detection of life will need astrophysicists and geologists to examine possible environments on other planets, engineers and physicists to design the missions and instruments that can collect data, and chemists and biologists to determine how to classify life,” JAXA’s Tasker says.
“But maybe that is appropriate: finding out what life really is and where it can flourish is the story of everyone on Earth. It should take all of us to unravel.”