There’s a space-age joke about a man who lost his car keys. He keeps looking under the nearest lamp post.
Asked why, he replied: “That’s where the light is.”
For millennia, we have looked up to the stars, haunted by the question: Are we alone? Our means of answering that question have been disappointingly limited.
To extend the joke’s metaphor, we are looking where the light is; where we are.
However, contrary to the joke, we’re not even sure the keys exist. (Although we’re reasonably sure they should.) We don’t know where the road leads, what’s in the next district, or exactly how we got to the lamppost to begin with.
It’s a mess.
Are we now ready to take a leap that can help us solve it?
We have the technology to look ahead. We have a clear understanding of what to look for.
The James Webb Space Telescope (JWST; built by the space agencies of the US, Europe and Canada), itself revolutionary, is already being overtaken by planned space telescopes with mirrors much larger than its 6.5-metre one.
Back on Earth, we are using laboratory simulations and computer simulations to help narrow down the list of biosignatures and conditions that might indicate living or long-extinct life.
“We started reaching out to other stars in 1995 and now we know that there are 200 billion Sun-like stars in our galaxy alone, glowing with billions of possibilities,” said Austrian astronomer and astrobiologist Lisa, founding director of the Carl Sagan Institute at Cornell University and author of Alien Earths: The Science for Planet Hunting in the Cosmos (2024). Kaltenegger says. “At this point, it would be a bigger surprise to learn that there is no life out there than to learn that there is life.”
What might such a life look like?
In The Hitchhiker’s Guide to the Galaxy, that wonderful, whimsical series of novels by Douglas Adams, it turns out that the universe is a bustling place full of bureaucracy, power struggles, infrastructure nightmares, broken hearts, despair, restaurants, and spaceships. Everyone is surprised that Earth did not detect it.
In the scientific world, this is called the Zoo hypothesis, and it matches up well with the Fermi Paradox (posited by physicist Enrico Fermi in 1950). The paradox is as follows: Given how much of the universe there is, it is highly likely that intelligent life (other than ours) exists, and yet we have seen no evidence of it.
The zoo’s hypothesis is that life there is simply waiting for this remote tribe to take hold, in the meantime living out of sight, like zoo keepers in wildlife conservation.
Is this why we are still “alone”? There are three other interesting theories left to consider while we’re at it.
1) It’s all a simulation, and the intelligent life we’re looking for is actually running the program we’re in. (This is a bit much, but serious money is being poured into research to prove that this is true. The logic of this theory includes the idea that “nothing can run faster than time” indicates the presence of a processor with a limited capacity. Are we in a kind of matrix? Interestingly, there is no way to disprove the theory.)
2) Life is an aberration, like the fungus on bread in the fridge. It was not supposed to exist. Somehow it happened, it would eventually do its thing, and then, the universe’s many revolving fridge shelves would once again be sterile.
3) We are in a hurry. We somehow picked up our weapons and now we are alone here. We think we’re watching, but really all we’re doing is waiting. Eventually, the rest of the universe will come to life. One will pass the place that was once our home, which is now a snowy dwarf, and think: “There is no point stopping there. There is clearly nothing to see there.”
Speculation aside…
What signals are we examining?
The US National Aeronautics and Space Administration (NASA) has a definition that currently serves as a guiding framework in the search: life is defined as “a self-sustaining chemical system capable of Darwinian evolution”.
Not knowing where to look (beyond a vague notion that life possibly exists in the Goldilocks zone of planets like ours), we have reached the point where we now know it is only a possibility.
It now appears that a frozen tundra planet, with the right biosignatures in its atmosphere, may indicate that it once contained life. We are using telescopes, spectroscopes, and a variety of instruments and algorithms to analyze gas signatures in exoplanet atmospheres, looking for such signals.
In the vastness of space, the challenge is knowing where to look – and even when.
“For about half of its 4.5 billion-year history, Earth’s atmosphere showed none of the clear signs of life we’re looking for (a substantial combination of oxygen and methane), although life existed at least 3.5 billion years ago,” says Kaltenegger.
About 2.4 billion years ago, oxygen levels had increased so much that the atmosphere had changed.
She adds, “We will need to be really lucky to get the signatures we are looking for, because we will need to be in exactly the right place, at the right time.”
Where are we looking?
In April, a team of scientists led by Indian-British astronomer Nikku Madhusudan of the Institute of Astronomy at the University of Cambridge detected signatures of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) swirling in the atmosphere of the distant planet K2-18b.
On Earth, these gases are produced only by organic matter (such as phytoplankton).
This discovery was welcomed with great enthusiasm. In an interview with Wknd, Madhusudan explained that he was not expecting the findings to actually give rise to life forms; For more information about the reason for such signatures. Still, he said, the possibility of life cannot be ruled out.
In July, researchers at NASA’s Jet Propulsion Laboratory found that the evidence for the existence of DMS was inconclusive. The search is on.
JWST is currently studying a fascinating planetary system called TRAPPIST-1, which was discovered in 2017 and contains seven Earth-sized worlds. “They orbit their red star at different distances, making them perfect Goldilocks test cases,” Kaltenegger writes in his book.
One of these planets, the fourth from its Sun, TRAPPIST-1e, is just 40 light-years away and shows signs of an atmosphere; Water in itself is a very rare indication of the potential for a healthy greenhouse effect.
“A little greenhouse effect goes a long way,” Nicole Lewis, associate professor of astronomy at Cornell University, said in a NASA statement. A working hypothesis suggests that water may exist in the form of a large ocean, with ice covering the rest of the planet. Further investigation is underway.
Much closer to home, two small rocky moons are being considered.
Jupiter’s Europa and Saturn’s Enceladus have potentially habitable oceans beneath layers of ice.
The European Space Agency’s JUICE (Jupiter Icy Moons Explorer) mission departs from Earth in 2023 and will begin its flight to Europa in 2032. NASA’s Europa Clipper mission launches in 2024 and is scheduled to arrive in 2030. (Both are orbiter missions; lander missions to these moons are still in the early planning stages.)
A long time ago and a galaxy far, far away
Orbiters and rovers make most of the news, but they’re not the only ones doing the heavy lifting.
The Hubble Space Telescope, built by NASA and the European Space Agency (ESA), completed 35 years in orbit this year. It was recently used to study the exoplanets TRAPPIST-1b and TRAPPIST-1c. (Exoplanets are planets outside our solar system.)
NASA’s Kepler space telescope, launched in 2009 and retired in 2018, discovered thousands of exoplanets. Madhusudan’s discovery was, in fact, partly based on Kepler data; Researchers around the world continue to use the information gathered from it.
NASA’s Spitzer space telescope, launched in 2003, discovered TRAPPIST-1.
JWST, launching in 2021, is looking back billions of years.
new Horizons
There is still more to come.
NASA’s Nancy Grace Roman Space Telescope, scheduled to launch in 2027, will be able to survey a sky area 100 times larger than the Hubble Space Telescope and JWST.
A more advanced version of JWST, NASA’s Habitable Worlds Observatory, is being designed for launch in the 2040s.
ESA’s proposed Large Interferometer for Exoplanets (Life) mission will use a constellation of artificial satellites to scan the thermal emissions of exoplanets for specific biosignatures.
Meanwhile, we continue to listen closely through programs like Breakthrough Listen, launched by England’s Stephen Hawking in 2015, and the US-based nonprofit SETI, or Search for Extra-Terrestrial Intelligence.
Is the answer here at home?
Is the Earth really just “a speck of dust suspended in a sunbeam,” as astronomer Carl Sagan said? Of course, it’s not just loneliness or the eternal desire for exploration that motivates us.
“We started looking for life elsewhere to understand how planets like Earth work,” says Kaltenegger.
Each discovery tells us more about who we are, and where our planet can go.
During our exploration, we may find ways to attract resources from space and reduce some of the stress on Earth. We can gather new knowledge about deflecting asteroids and dealing with pollution, says Kaltenegger.
There is also a chance that we may get sentient life. Ultimately it is theorized that the early organic molecules that led to life on Earth were thrown here via asteroid. This means that there may be other developments as well.
Of course, it could also mean that we’ve already met one kind of alien: us.
