How Astrobiology’s Fortunes Swung Back and Forth – and Back Again


Four moons huddle near Saturn’s multi-hued disk in this image by the Cassini probe, October 9, 2008. Photo: NASA/JPL/Space Science Institute.

In Manu Joseph’s novel Serious Men (2010), recently made into a movie by Netflix, an astrophysicist at the Indian Space Research Organisation is dissatisfied with the assumptions science has thus far made: that the technologies and appearance of extraterrestrial life would be human-like. Acharya’s own great idea is that alien life in space is much more likely to be microbial, so he kicks off a mission with a giant space-balloon that has containers designed to trap some of these tiny aliens.

Within the novel, this experiment also fails to find aliens – but through this contrast Joseph brings out the role of human perception and philosophical baggage in our search for extraterrestrial life.

In January 2021, a book entitled Extraterrestrial was published, authored by Harvard University astronomy professor Avi Loeb. In the book, Loeb claimed that ‘Oumuamua, an interstellar asteroid that entered our Solar System in 2017, behaved in a way that could be best explained by assuming that it was the work of intelligent extraterrestrial designers. Loeb has maintained that it was “the first sign of intelligent life beyond Earth” – but his hypothesis has been met with derision from the wider scientific community.

His detractors have argued that Loeb is doing science a disservice by contributing to the giggle factor – an attitude in the public of responding to claims about extraterrestrial life with incredulity and laughter – with his idea, especially considering ‘Oumuamua’s behaviour can be explained without invoking alien intelligence. For his part, Loeb said in an interview with Scientific American that his “colleagues are not using common sense”. Excerpt:

Based on data from NASA’s Kepler mission, roughly half of the galaxy’s sunlike stars have a planet about the size of Earth, at about the same distance of Earth from the Sun, so that you can have liquid water on the surface and the chemistry of life as we know it. So if you roll the dice on life billions of times in the Milky Way, what is the chance that we are alone? Minuscule, most likely!

In an article published a year after his demise in 1996, Carl Sagan made a similar argument: “There can be little doubt that civilisations more advanced than Earth’s exist elsewhere in the universe”.

The prospect of flourishing extraterrestrial life has donned the giggle factor only in recent years, thanks to sci-fi films and novels that have made aliens seem as outlandish as commonplace.

One article published in February 2021 discussed “just how much our philosophical mood has changed back and forth across the centuries” vis-à-vis intelligent extraterrestrial life. According to its author, astronomer Caleb Scharf, people accepted the idea of intelligent life elsewhere in the universe as “fact” through the 16th to the 20th centuries, and cites examples of famous astronomers who believed in the philosophy of life being everywhere in the cosmos.

This philosophical attitude was the product of the Copernican revolution – which displaced Earth from the centre of the universe, and its privileged place in man’s imagination. Before this, philosophers in the west believed the ‘Heavens’ and ‘Earth’ were distinct realms. As Scharf writes, a flurry of technological advancements in the 16th century allowed investigators of the natural universe, and others, to consider that there could be planets around other stars, and moons around those planets, like in our Solar System. This then led to popular speculation that there could be life there as well.

As science writer Mark Kaufman wrote, scientists continued to assume this was the case until NASA launched the ‘Viking’ missions to Mars in 1975 and 1976. One of the mission’s objectives was to search for evidence of past life on Mars. They carried some instruments to help with this task. One of them, according to its principal investigator Gilbert Levin, apparently found evidence of metabolism (active life). But scientists found with subsequent analysis and more data that this finding didn’t hold up.

Also read: The Perseverance Rover Is NASA’s Big Move to Search for Life on Mars

Then, in 1996, CNN reported that researchers at NASA had found signs of past life on a meteorite from Mars – again eventually debunked. Together with science’s continuing inability to explain the phenomenon of life itself, scientists had a surprisingly hard time explaining what turned organic molecules into the self-replicating precursors of life.

At the same time, the Search for Extraterrestrial Intelligence hadn’t turned up any extraterrestrial signs of life despite having scanned the skies from the mid-1980s and millions of dollars in investment.

These developments turned the philosophical tide about life out there, as Scharf writes, “from one extreme to the other”. At the heart of this turn was Enrico Fermi’s paradox – an expression of the contradiction between the estimated chance of there being extraterrestrial life and our inability to find it.

In our present moment, the question “are we alone?” features prominently in our philosophical deliberations about our own presence in the universe, more so than it has in a few centuries.

The amount of funding dedicated to research in astrobiology dried up between the 1990s and 2010, so much so that an article in Science magazine in 2007 said the field was “fighting for its life”.

Fortunately, in the last decade, we have discovered thousands of exoplanets and have perfected new ways of observing distant stars and planetary systems, leading – by one account – to an “extraterrestrial renaissance”. The NASA Curiosity rover, which landed on Mars in 2012, was the agency’s first mission with an explicitly astrobiological mission since the 1990s. With newer Mars missions actively searching for signs of life once more, the tide seems to be turning again.

That said, contemporary investigations of extraterrestrial life are still based, to varying degrees, on what we know about life Earth. For example, we think to look for signs of life on other planets when there are signs of water because water implies life on Earth. The same goes for oxygen – even though it can be formed in processes that don’t involve life.

In the absence of other forms of life, assumptions based on ourselves can’t help but inform our search for the ‘other’. As such, the spectrum of parameters in the vast universe we have been able to cover so far in our search is like “looking in a hot tub of water to draw conclusions about the contents of Earth’s oceans,” as one paper put it.

But this is not likely to discourage astrobiologists. As the search for extraterrestrial life moves once again into the limelight, the paucity of immediate results isn’t likely to induce one more swing of the philosophical pendulum.

Binit Priyaranjan is a student of literature at the Delhi University and a freelance writer.