JWST has shown that it can detect the fingerprints of life on exoplanets

components of life spread all over the universe. Although Earth is the only known place in the universe where life exists, the discovery of extraterrestrial life The main objective From modern astronomy and the planetary science.

We are two scholars studying outer planets and the astrobiology. Thanks in large part to next-generation telescopes like James Webb, researchers like us will soon be able to measure the chemical composition of the atmospheres of planets around other stars. Hopefully, one or more of these planets will have a chemical fingerprint for life.

Habitable outer planets

to live It may exist in the solar system Where there is liquid water – such as aquifers on Mars or in the oceans of Jupiter’s moon Europa. However, the search for life in these places is very difficult as it is difficult to access and in order to detect life, a probe must be sent to return the physical samples.

Many astronomers believe that there is a file Good chance of life on planets orbiting other starsThis could be the place Life will be found first.

Theoretical calculations suggest that there is something nearby 300 million potentially habitable planets Only in the Milky Way and Many habitable planets the size of Earth Within only 30 light years from Earth – mankind’s neighbors in the galaxy. So far, astronomers have done it Discover more than 5,000 exoplanetsIncluding hundreds of potentially habitable ones, using indirect methods which measures how a planet affects its nearby star. These measurements can provide astronomers with information about the mass and size of an exoplanet, but no more than that.

Looking for bio signatures

To discover life on a distant planet, astrobiologists will study existing starlight Interaction with the planet’s surface or atmosphere. If the atmosphere or surface is transformed by life, the light may contain evidence called a “biosignature”.

During the first half of its existence, the Earth had an atmosphere devoid of oxygen, although unicellular life existed. The Earth’s biometric footprint was very weak in this early era. That suddenly changed 2.4 billion years ago Then a new family of algae arose. The algae used photosynthesis that produces free oxygen – oxygen that is not chemically bound to any other element. Since that time, Earth’s oxygen-filled atmosphere has left a strong and easily distinguishable bio-imprint on the light passing through it.

When light reflects off the surface of a material or passes through a gas, certain wavelengths are more likely to be trapped in the gas or surface of the material than others. This selective modification of the wavelengths of light is the reason for the different colors of objects. Leaves are green because chlorophyll is particularly good at absorbing light in the red and blue wavelengths. When light hits the paper, the red and blue wavelengths are absorbed, causing most of the green light to bounce back into your eyes.

The pattern of lost light is determined by the specific composition of the material with which the light interacts. For this reason, astronomers can learn about the composition of an exoplanet’s atmosphere or surface by measuring the specific color of light coming from a planet.

This method can be used to determine the presence of certain atmospheric gases associated with life – such as oxygen or methane – because these gases leave very specific signals in the light. It can also be used to detect strange colors on the surface of the planet. For example, on Earth, plants use chlorophyll and other pigments and algae in photosynthesis at specific wavelengths of light. These dyes Distinctive color production It can be detected using a sensitive infrared camera. If you see this color reflecting off the surface of a distant planet, it probably indicates the presence of chlorophyll.

Telescopes in space and on Earth

It takes an incredibly powerful telescope to detect these subtle changes in the light of a potentially habitable exoplanet. Currently, the only telescope capable of such a feat is the New Telescope James Webb Space Telescope. as it is Scientific operations have begun In July 2022, James Webb gave a wonderful lecture Gas giant exoplanet WASP-96b. The spectrum showed the presence of water and clouds, but a large, hot planet like WASP-96b is unlikely to harbor life.

However, these early data show that James Webb is able to detect weak chemical signals in light from exoplanets. For the next few months, Webb was turning her mirrors TRAPPIST-1stA potentially habitable Earth-sized planet just 39 light-years from Earth.

Webb can search for biometrics by studying and recording planets as they pass in front of their host stars Starlight streams through the planet’s atmosphere. But Webb wasn’t designed to search for life, so the telescope is only capable of examining some of the closest potentially habitable worlds. It can also detect changes made to: Levels of carbon dioxide, methane and water vapor in the atmosphere. Although certain combinations of these gases can suggest lifeWebb cannot detect the presence of unbound oxygen, which is the strongest indicator of life.

Pioneering concepts for future space telescopes, and even more powerful, include plans to block bright light from Mother Earth’s star to detect starlight reflected off the planet. This idea is similar to using your hand to block sunlight in order to see something better from a distance. Future space telescopes could use small internal masks or a large parachute-like spacecraft for this purpose. Once the starlight is blocked out, it becomes much easier to study the light reflected off a planet.

There are also currently three massive ground-based telescopes under construction that will be able to search for biometric fingerprints: Giant Magellan TelescopeThe Thirty meters telescope and the european very large telescope. Each is much more powerful than Earth’s telescopes, and although hampered by Earth’s atmosphere distorting starlight, these telescopes may be able to explore the atmospheres of the nearest worlds in search of oxygen.

Is it biology or geology?

Even using the most powerful telescopes in the coming decades, astrobiologists will only be able to detect the powerful biosignatures produced by worlds completely altered by life.

Unfortunately, most of the gases released by terrestrial life can also be produced through non-biological processes – cows and volcanoes release methane. Photosynthesis produces oxygen, but sunlight also occurs when it splits water molecules into oxygen and hydrogen. there A good opportunity for astronomers to discover some false positives In search of a distant life. To rule out false positives, astronomers need to understand an interesting planet well enough to understand if it is. Geological or atmospheric processes can mimic a biosignature.

The next generation of exoplanet studies has the potential to increase the level of Unusual evidence The need to prove the existence of life. The first release of data from the James Webb Space Telescope gives us an idea of ​​the exciting progress coming soon.

Chris AmbekDistinguished University Professor of Astronomy, University of Arizona and the Daniel AbayProfessor of astronomy and planetary sciences, University of Arizona

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