Researchers spy signs of life in exoplanet atmospheres

The next generation of advanced telescopes could step up the hunt for potential extraterrestrial life by closely peering into the atmospheres of nearby exoplanets, new research suggests.

Recently published in The astronomical journal, a paper details how a team of astronomers from Ohio State University examined the ability of upcoming telescopes to detect chemical traces of oxygen, carbon dioxide, methane and water on 10 rocky exoplanets. These elements are biosignatures also present in Earth’s atmosphere and can provide key scientific evidence of life.

The study found that for two of these nearby worlds, Proxima Centauri b and GJ 887 b, these telescopes are very adept at detecting the presence of potential biosignatures. Of the two, the results show that only for Proxima Centauri b would the machines be able to detect carbon dioxide if it were present. Although no exoplanets have been found that precisely match Earth’s earliest conditions, this work suggests that if examined in more detail, these unique super-Earths – planets more massive than Earth but smaller than Neptune – could constitute a suitable target for future research missions.

To advance the search for habitable planets, Huihao Zhang, lead author of the study and senior astronomy researcher at Ohio State, and his colleagues also sought to determine the effectiveness of specialized imaging instruments such as the James Webb Space Telescope (JWST) and other extremely large telescopes (ELTs) such as the European Very Large Telescope, the Thirty Meter Telescope, and the Giant Magellan Telescope can directly image exoplanets.

“Not all planets are amenable to direct imaging, but that’s why simulations give us a rough idea of ​​what ELTs would have delivered and what promises they are expected to keep once built,” Zhang said .

The direct method of imaging exoplanets involves using a coronagraph or starshade to block the light of a host star, allowing scientists to capture a faint image of the new orbiting world. But since locating them this way can be difficult and time-consuming, the researchers set out to see how well ELT telescopes could meet this challenge.

To do this, they tested the ability of each telescope’s instruments to differentiate the universal background noise from the planetary noise they aimed to capture while detecting biosignatures; called signal-to-noise ratio, the higher it is, the more easily a planet’s wavelength can be detected and analyzed.

The results showed that the direct imaging mode of one of the European ELT instruments, called the Mid-Infrared ELT Imager and Spectrograph, worked best for three planets (GJ 887 b, Proxima b and Wolf 1061 c) to discern the presence of methane, carbon, carbon dioxide and water, while its monolithic optical full-field spectrograph instrument with high angular resolution and near infrared could detect methane, carbon dioxide, oxygen and l water, but required a much longer exposure time.

Additionally, because these findings involved instruments that will need to peer into the chemical fog of Earth’s atmosphere to advance the search for cosmic life, they were compared to the JWST’s current space capabilities, Zhang said.

“It’s hard to say whether space telescopes are better than ground-based telescopes, because they are different,” he said. “They have different environments, different locations and their observations have different influences.”

In this case, the results revealed that although GJ 887 b is one of the most suitable targets for direct ELT imaging, its location and size results in a particularly high signal-to-noise ratio, for some planets in transit, such as TRAPPIST-1. system, JWST techniques for studying planetary atmospheres are more suited to detecting them than direct imaging from ELTs on Earth.

But because the study took a more conservative assumption with the data, Zhang said, the true effectiveness of future astronomical tools could still surprise scientists. And subtle contrasts in performance aside, these powerful technologies serve to expand our understanding of the universe and are meant to complement each other, said Ji Wang, study co-author and assistant professor of astronomy at Ohio State . That’s why studies like this one, which assess the limits of these technologies, are needed, he said.

“The importance of simulation, especially for missions that cost billions of dollars, cannot be emphasized enough,” Wang said. “Not only do people have to build the hardware, but they also work to simulate the performance and be ready to achieve these glorious results.”

In all likelihood, because ELTs won’t be completed until the end of the decade, researchers’ next steps will be to simulate the ability of future ELT instruments to study the intricacies of evidence of rampant life on our own planet.

“We want to see how much detail we can study our atmosphere and how much information we can extract from it,” Wang said. “Because if we can’t answer questions of habitability with Earth’s atmosphere, there’s no way we can begin to answer these questions around other planets.”