Whether we are alone in the universe is one of the biggest questions in science.
A recent study, led by astrophysicist Nikku Madhusudhan at the University of Cambridge, suggests that the answer might be no. Based on observations of NASA’s James Webb Space Telescope, the research into extraterrestrial life points to K2-18B, a distant exoplanet 124 light years from the earth.
The researchers found strong proof of a chemical called Dimethylsulfide (DMS) in the atmosphere of the planet. On earth, DMS is only produced by living organisms, so it seems like a mandatory sign of life, or “biosignature”.
Although the new findings have reached the headlines, a glance at the history of astrobiology shows that similar discoveries in the past have not been decisive. The issue is partly theoretical: scientists and philosophers still have no agreed definition of exactly what life is.
A closer look
In contrast to the older Hubble telescope, which revolves the earth around the earth, NASA’s James Webb Space Telescope is placed around the sun. This gives it a better picture of objects in deep space.
When distant exoplanets pass for their hostess, astronomers can distract what chemicals are in their atmospheres of the multi -wavelengths they leave in the detected light.
Since the precision of these measurements can vary, scientists estimate an error margin for their results to exclude random opportunity. The recent study of K2-18B found only a probability of 0.3% that the measurements were a fluke, so that researchers had faith in their detection of DMs.
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On earth, DMS is only produced by life, usually aquatic phytoplankton. This makes it a convincing biosignature.
The findings are in line with what scientists already assume about K2-18B. Considered as a “Hycean” world (a portmanteau of “hydrogen” and “ocean”), it is thought that K2-18B has a hydrogen-rich atmosphere and a surface covered with liquid water. These conditions are beneficial for life.
So does this mean that the oceans of K2-18b crawl with alien microbes?
Some experts are less certain. Speaking of the New York Times, expressed planetary scientist Christopher Glein doubted that the study represents a “smoking gun”. And experiences from the past teach us that in astrobiology non -striking findings are the norm.
Life as we don’t know
Astrobiology has its origins in efforts to explain how life started on our own planet.
In the early 1950s, the Miller-Erey experiment showed that an electric current could produce organic compounds of a best-guess reconstruction of the chemistry in the earliest oceans of the earth-Soms called the “original soup”.
Although it did not give a real indication of how life in fact evolved for the first time, the experiment left astrobiology with a framework for investigating the chemistry of alien worlds.
In 1975 the First Mars Landers – Viking 1 and 2 – conducted experiments with collected monsters from Mars -Grand. In one experiment, nutrients seemed to produce carbon dioxide soil samples, suggesting that microbes consumed the nutrients.
The first excitement disappeared quickly, because other tests do not grab organic compounds in the soil in the soil. And later studies identified plausible non-biological explanations for the carbon dioxide.
One explanation points to a mineral abundantly to Mars called perchlorate. Interactions between perchlorate and cosmic rays may have led to chemical reactions that are comparable to those observed by the Viking tests.
Concerns that were infected by the instruments of the landers on earth also introduced uncertainty.
In 1996, a NASA team announced a Martian meteorite that was discovered in Antarctica Boring signs of the past of alien life. Specimen ALH84001 showed proof of organic hydrocarbons, as well as magnetics crystals arranged in a distinctive pattern that was only produced organically on earth.
More suggestive were the small, round structures in the rock that resemble fossilized bacteria. Again, closer analysis led to disappointment. Non-biological explanations were found for the magnetite grains and hydrocarbons, while the fossil bacteria were considered too small to support life plausibly.
The most recent similar discovery – claims from phosphinegas on Venus in 2020 – is also still controversial. Phosphine is considered a biosignature, because it is produced on earth by bacterial life in environments with low oxygen, especially in the digestive channels of animals. Some astronomers claim that the detected phosphine signal is too weak, or is due to inorganically produced sulfur compounds.
Every time biosa signatures are found, biologists confront the ambiguous distinction between life and non-life, and the difficulty of extrapolating characteristics of life on earth to alien environments.
Carol Cleland, a leading philosophy of science, has called this the problem to “find life as we don’t know”.
Then control chemistry
We still know very little about how life originated on earth for the first time. This makes it difficult to know what to expect from the primitive life forms that can exist on Mars or K2-18B.
It is uncertain whether such life forms would look like earth life at all. Outward life can manifest itself on surprising and unrecognizable ways: although life on earth is based on carbon, cellular and dependent on self -replexing molecules such as DNA, an extraterrestrial life form can fulfill the same functions with completely unknown materials and structures.
Our knowledge of the environmental conditions on K2-18B is also limited, so it is difficult to imagine the adjustments that a Hycoatic organism needs to survive there.
Chemical biosa signatures derived from life on earth, it seems that a misleading guide can be.
Philosophers of biology claim that a general definition of life should go than chemistry. According to one vision, life is determined by the organization, not the list of chemicals that come up with: living creatures embody a kind of self -organization that is able to produce its own parts autonomously, maintain a metabolism and maintain a border or membrane that separates itself from outside.
Some philosophers of science claim that such a definition is too inaccurate. In my own research I have argued that this kind of generality is a power: it helps to keep our theories flexible and to apply to new contexts.
K2-18B can be a promising candidate for identifying extraterrestrial life. But excitement about biosa signatures such as DMS mommens deeper, theoretical problems that must also be solved.
New life forms in distant, unknown environments may not be detectable in the ways we expect. Philosophers and scientists will have to work together on non-reductive descriptions of living processes, so that we will not miss it when we encounter extraterrestrial life.
Campbell Rider, PhD candidate in philosophy – Philosophy of biology, University of Sydney
This article has been re -published from The conversation Under a Creative Commons license. Read the Original article.
