The James Webb Space Telescope is humankind's most sophisticated telescope to date. We have seen the capabilities of Webb in the latest release of images of the cosmos. But what can Webb do for the search of extraterrestrial life? Can Webb help us study distant planets and figure out if there is life on them?
The James Web Space Telescope has already revolutionized the way we look at the universe and has only delivered a few deep space images. However, despite only beginning to explore the cosmos, scientists worldwide can be more than excited about what Webb will help reveal.
Not only will Webb — Hubble’s official successor — deliver unprecedented images of our universe, but it is a key tool that astronomers will use to find out more about the universe. Scientists will use Webb to comb through the cosmos and look for key ingredients for life that are spread across the vastness of space.
If we want to detect life beyond Earth- a major goal of modern astronomy and planetary science- then Webb will certainly help, even though it is not specifically designed to search for alien life.
Webb can do a LOT for scientists studying alien worlds and astrobiology.
In fact, state-of-the-art telescopes such as Webb will allow researchers an unprecedented view into the chemical composition of the atmospheres of distant exoplanets and their star system.
Scientists could discover a chemical signature of life on one of the many exoplanets discovered to date, and Webb could be the tool that made it possible.
But to find out where we are truly alone in the universe, we need not look for star systems far away. In fact, many scientists believe that life, as we know it, may even exist in the solar system, practically anywhere where liquid water exists. One such example would be Mars.
Although the Red Planet is barren and hazardous for life on the surface, beneath the surface, in aquifers deep beneath Mars, life could probably thrive.
Another great place to search for alien life is the moons of Saturn and Jupiter. Europa, for example, is one of the most promising candidates for alien life to exist.
Searching for life in these places is extremely challenging because they are difficult to reach, and physical samples would need to be returned to detect life.
And even if we find evidence that only Earth is habitable in the entire solar system, many experts believe that there are reasonable chances that life has sprung into existence on planets that orbit distant stars.
What’s even more interesting is that according to our best estimates, there could be between 100 and 300 million habitable planets in the Milky Way galaxy alone.
The indirect methods of measuring how a planet affects its nearby star have assisted in the discovery of more than 5000 exoplanets, including hundreds that are potentially habitable. These measurements can determine exoplanet mass and size, but little else is known about them.
Atmosphere is key
To find out what a planet is like, astronomers look at the atmosphere and the light spectrum.
Astronomers study the interaction between starlight and planet surfaces and atmospheres to detect life on distant planets. Light can carry a clue, known as a “biosignature,” if the atmosphere or surface was transformed by life.
Even though Earth hosted simple, single-celled life, it had an atmosphere without oxygen for the first half of its existence. As a result, its biosignature was faint at this early stage of Earth’s evolution. All that changed abruptly when a new algae family evolved 2.4 billion years ago.
Algae photosynthesize by creating free oxygen, meaning oxygen that is not chemically bound to any other element. Since then, Earth’s oxygen-filled atmosphere has left behind a biosignature that can be easily detected by light passing through it.
The wavelengths of light that bounce off a surface or pass through a gas remain more trapped than others. As a result, objects have different colors because of this selective trapping of light wavelengths.
Consider leaves as an example. The chlorophyll in leaves absorbs light especially well in the red and blue wavelengths. Therefore, most of the light that hits a leaf is reflected in green color since the red and blue wavelengths are absorbed.
Light interacts with materials in specific ways, resulting in unique patterns of missing light. By measuring the particular color of light coming from an exoplanet, astronomers can learn something about its atmosphere or surface.
A very specific light signature is left by certain atmospheric gases associated with life, such as oxygen or methane, which can be detected using this method. It could also detect strange colors on a planet’s surface.
For example, in plants and algae, chlorophyll captures specific wavelengths of light during photosynthesis. A sensitive infrared camera can detect the characteristic colors of these pigments. The presence of chlorophyll on a distant planet could be indicated by this color reflected off its surface. In the same way, distant alien astronomers currently exploring the cosmos, wondering whether there is intelligent life, could point their telescope to Earth and find tell-tale signs that hint at life on Earth.
However, detecting these subtle changes in light coming from a potentially habitable exoplanet requires an incredibly powerful telescope. The new James Webb Space Telescope is currently the only telescope capable of such a feat.
How James Webb can help us find alien life
In July 2022, James Webb began science operations by taking a reading of the spectrum of WASP-96b, an exoplanet with a gas giant atmosphere. Water and clouds were detected in the spectrum, but life is unlikely to exist on a planet as large and hot as WASP-96b.
In spite of this, James Webb has shown that faint chemical signatures can detect light from exoplanets. As part of its planned mission, Webb will focus its cameras on TRAPPIST-1e, a potentially habitable planet 39 light-years away.
When a planet passes in front of its host star, Webb can capture the starlight that filters through its atmosphere to observe biosignatures. The Webb telescope, however, was not designed to search for life, so it can only observe a few of the nearest potentially habitable planets.
But that may be more than enough.
Additionally, it can detect only changes in carbon dioxide, methane, and water vapor levels in the atmosphere. It is not possible for Webb to detect unbonded oxygen, the most powerful signal of life, although certain combinations of these gases may suggest life. At the beginning of the Paleoproterozoic, unbound oxygen (also called molecular dioxygen, O2) was first found on Earth in large quantities
A more powerful telescope than Webb
If we want to find out whether we are alone in the universe, then we need a better tool, more suitable for the specific task. And the key to looking for life on distant planets is blocking light.
In the future, with even more powerful telescopes, starlight reflected by a planet’s surface will be revealed by blocking the star’s bright light. It’s like shading something in the distance with your hand to see better.
Future space telescopes may use small, internal masks to accomplish this since studying light bouncing off a planet becomes much easier once the starlight is blocked.
However, we do not necessarily need to send telescopes into space to determine whether distant exoplanets show signatures of life.
In fact, three massive ground-based telescopes currently under construction, the Giant Magellan Telescope, the Thirty Meter Telescope, and the European Extremely Large Telescope, could prove to be the ultimate tools for astronomers to answer whether we are alone in the universe.
These telescopes are far more powerful than any existing telescope on Earth.
Astrobiologists will only be able to detect biosignatures on planets that are completely transformed by alien life, even with the most powerful telescopes of the next few decades.
Methane is one of the most common gases released by terrestrial life, but the process of methane production can also be attributed to non-biological processes.
This means that if astronomers search for distant life and detect a signal that is indicative of life, it could be a false positive. To eliminate false positives, astronomers must understand a planet well enough to identify whether its atmospheric or geologic processes are similar to a biosignature.
Exoplanet studies could one day pass the bar needed to prove life’s existence by providing the extraordinary evidence needed. As we look forward to the rich discoveries coming from the James Webb Space Telescope, the first data release from the telescope gives us a sense of what’s to come.
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