JWST Shows It Can Detect Signatures of Life on Exoplanets

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ConversationThey are ingredients for life spread throughout the universe. Although Earth is the only known place in the universe with life, the discovery of life beyond Earth a main goal of modern astronomy and planetary science.

We are two learning scientists exoplanets and astrobiology. Thanks in large part to next-generation telescopes like the James Webb, researchers like us will soon be able to measure the chemical composition of the atmospheres of planets around other stars. The hope is that one or more of these planets will have the chemical signature of life.

There are many known exoplanets in the habitable zones—not too close to a star where water boils, but orbiting close enough that the planet is a frozen solid—marked in green for both the solar system and the Kepler-186 star system with its planets. labeled b, c, d, e and f. Image credit: NASA Ames / SETI Institute / JPL-Caltech / Wikimedia Commons

Habitable exoplanets

Life It may exist in the solar system where there is liquid water – like underground water layers on Mars or in the oceans of Jupiter’s moon Europa. However, searching for life in these places is extremely difficult because they are difficult to reach and detecting life requires sending a probe to return physical samples.

Many astronomers believe there is the chance of life existing on planets orbiting other starsand possibly where the first life will be found.

Theoretical calculations show that around 300 million potentially habitable planets Alone in the Milky Way galaxy and several habitable Earth-sized planets Just 30 light-years from Earth – actually humanity’s galactic neighbors. Until now, there are astronomers Discovered more than 5000 exoplanetsincluding potential uses for hundreds of dwellings indirect methods measures how a planet affects a nearby star. These measurements can tell astronomers about the exoplanet’s mass and size, but little else.

Each material absorbs specific wavelengths of light, as shown in this diagram depicting the wavelengths of light most readily absorbed by different types of chlorophyll. Image credit: Daniele Pugliesi / Wikimedia Commons, CC BY-SA

Searching for biosignatures

To detect life on a distant planet, astrobiologists will study starlight interacts with the planet’s surface or atmosphere. If the atmosphere or surface has been modified by life, the light may carry a clue called a “biosignature.”

During the first half of its existence, Earth had an oxygen-free atmosphere, despite having simple, single-celled life. During this early period, Earth’s biosignature was very weak. That suddenly changed 2.4 billion years ago when a new algal family develops. Algae used the process of photosynthesis, which produces free oxygen – oxygen that has no chemical bond with any other element. Since then, Earth’s oxygen-rich atmosphere has left a strong and easily detectable biosignature in the light passing through it.

When light bounces off the surface of a material or passes through a gas, certain wavelengths of light are more likely to be trapped at the surface of the gas or material than others. This selective capture of wavelengths of light is why objects have different colors. Leaves are green because chlorophyll is particularly good at absorbing light in the red and blue wavelengths. When light hits a leaf, the red and blue wavelengths are absorbed, leaving mostly green light to return to your eyes.

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

This method can be used to recognize the presence of certain atmospheric gases associated with life – such as oxygen or methane – because these gases leave very specific traces in light. It can also be used to detect peculiar colors on the planet’s surface. On Earth, for example, chlorophyll and other pigments capture certain wavelengths of light that plants and algae use for photosynthesis. These pigments produces characteristic colors can be detected using a sensitive infrared camera. If you saw this color reflected off the surface of a distant planet, it would potentially indicate the presence of chlorophyll.

Telescopes in space and on Earth

The James Webb Space Telescope is the first telescope capable of detecting chemical signatures from exoplanets, but its capabilities are limited. Image credit: NASA / Wikimedia Commons

An incredibly powerful telescope is needed to detect these subtle changes in light from a potentially habitable exoplanet. So far, the only telescope capable of such a feat is a new one The James Webb Space Telescope. Like it began scientific operations In July 2022, James Webb took a reading of the spectrum gas giant exoplanet WASP-96b. The spectrum showed the presence of water and clouds, but a planet as large and hot as WASP-96b is unlikely to harbor life.

However, this preliminary data suggests that James Webb is able to detect faint chemical signatures in light from exoplanets. In the coming months, Webb is preparing to turn its mirrors TRAPPIST-1eA potentially habitable Earth-sized planet just 39 light-years from Earth.

Webb can search for biosignatures by scanning and capturing planets that pass in front of their stars. starlight filtering through a planet’s atmosphere. But Webb wasn’t designed to look for life, so the telescope can only scrutinize a few of the closest potentially habitable worlds. It can also only detect changes atmospheric levels of carbon dioxide, methane, and water vapor. Certain combinations of these gases life can offerWebb fails to detect the presence of unbound oxygen, the strongest signal for life.

Leading concepts for the future include plans to block the bright light of a planet’s host star so that even more powerful space telescopes can detect starlight reflected from the planet. The idea is similar to blocking sunlight with your hand to see something far away better. Future space telescopes may use small, inner masks or large, outer, umbrella-like spacecraft to do this. Once the starlight is blocked, it is easier to study the light bouncing off the planet.

There are also three giant ground-based telescopes currently under construction that could search for biosignatures: The Giant Magellan Telescopethe Thirty Meter Telescope and Europe’s largest telescope. Each is much more powerful than existing telescopes on Earth, and despite the ability of Earth’s atmosphere to distort starlight, these telescopes can probe the atmospheres of the nearest worlds for oxygen.

Animals, including cows, produce methane, but so do many geological processes. Image credit: Jernej Furman / Wikimedia Commons, CC BY

Is it biology or geology?

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

Unfortunately, most of the gases released by terrestrial life can also be produced by non-biological processes – both cows and volcanoes emit methane. Photosynthesis produces oxygen, but so does sunlight when it splits water molecules into oxygen and hydrogen. there is good luck astronomers will detect some false positives when looking for the distant life. To rule out false positives, astronomers must understand the planet of interest well enough that its geological or atmospheric processes can mimic a biosignature.

The next generation of exoplanet research has the potential to cross the line extraordinary evidence it is necessary to prove the existence of life. The first data release from the James Webb Space Telescope gives us a sense of the exciting progress to come.Conversation

Chris ImpeyDistinguished Professor of Astronomy at the University, University of Arizona and Daniel ApaiProfessor of Astronomy and Planetary Sciences, University of Arizona

This article is being republished Conversation Under Creative Commons license. read it original article.

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