Rocky, Earth-sized planets in our Milky Way may be surrounded by atmospheres, with new research indicating a strong possibility of liquid water on their surfaces, supporting the potential for life.
Two separate papers, to be released on Monday in the Astrophysical Journal Letters, focus on the TRAPPIST-1 system, which contains seven rocky planets orbiting a single star. Both studies present initial findings from NASA’s James Webb Space Telescope, suggesting that one planet, TRAPPIST-1e, could possess a nitrogen-rich atmosphere, although further research is necessary to confirm this.
These findings represent significant progress in the search for extraterrestrial life both within our solar system and beyond.
Recently, NASA revealed that rock samples from Mars may harbor evidence of ancient microorganisms. Presently, Mars has a thin atmosphere made primarily of carbon dioxide, nitrogen, and argon, but billions of years ago, it likely possessed a much thicker atmosphere that allowed liquid water to exist on its surface.
For quite some time, scientists have maintained that water is a crucial element for life.
For a planet or moon to retain water in liquid form, it must have an atmosphere that prevents instant evaporation into space. This makes the search for exoplanet atmospheres one of the most exciting and promising areas of astronomical research.
“Ultimately, our goal is to identify planets that can support life,” stated Ryan McDonald, an exoplanet astronomer at St Andrews University, Scotland, and co-author of both studies. “To do this, we first need to identify whether these planets have atmospheres.”
The TRAPPIST-1 system is located 40 light-years from Earth and has been extensively studied since its discovery in 2016, as some of its planets may have conditions suitable for extraterrestrial life.
One light year is approximately 6 trillion miles.
Specifically, TRAPPIST-1e is thought to reside in the so-called “habitable zone,” where liquid water could be present on the surface—not too close to the star to be scorching hot and not too far to freeze.
In a recent study, astronomers utilized NASA’s James Webb Space Telescope to observe four “transits” of TRAPPIST-1e, which occur when the planet passes in front of its star. While the telescope did not directly detect the planet’s atmosphere, it measured how light passing through the atmosphere was absorbed, if one is present.
Like a prism, light can be split into different color bands across the spectrum, and variations in how particular colors are filtered or absorbed can help identify the presence of specific atoms or gas molecules.
For instance, if a specific color is absorbed, it may indicate a high concentration of carbon dioxide, while other color changes could suggest the presence of hydrogen, oxygen, methane, or nitrogen.
“If no color variation is present, the planet is likely just a barren rock,” McDonald noted. “Barren rocks won’t show any color changes in response to light.”
During the four transits, researchers found no signs of a hydrogen-rich atmosphere surrounding TRAPPIST-1e, nor did they observe any indications of a carbon dioxide-rich atmosphere. However, observations from the Webb telescope suggest a potential nitrogen-rich atmosphere.
“This is an exciting development that will significantly narrow down the prospects for a more Earth-like atmosphere,” remarked Caroline Piaulett Graeb, a postdoctoral researcher at the University of Chicago who was not involved in the new research.
Earth’s atmosphere is composed of a significant amount of nitrogen gas. Titan, one of Saturn’s moons, has an atmosphere primarily made of nitrogen and is believed by NASA to harbor a vast underground sea. Although it may be habitable, the methane-rich environment of the moon differs greatly from conditions on Earth.
Piaulet-Ghorayeb, the lead author of a study published last month in the Astrophysical Journal, focused on another planet in the TRAPPIST-1 system, TRAPPIST-1d. This planet is also located within the habitable zone, but the study found no evidence of common Earth-like molecules such as water, carbon dioxide, or methane.
Studying these distant worlds poses significant challenges.
The TRAPPIST-1 star is small and exceptionally active, producing considerable background noise that complicates researchers’ efforts. McDonald and his team dedicated over a year to analyzing data from the Webb telescope in order to isolate and identify chemical signatures from TRAPPIST-1e and its star.
To confirm the presence of an atmosphere, McDonald and his colleagues plan to observe TRAPPIST-1e during an additional 15 transits over the coming years.
They are also looking into three other planets, TRAPPIST-1f, TRAPPIST-1g, and TRAPPIST-1h, which are located further out in the system.
This research aims to bring scientists closer to answering some of the most persistent questions regarding exoplanets and the existence of life.
“We have not yet reliably confirmed the atmosphere of rocky planets outside our solar system, but it opens the door to studying temperate planets,” said Piaulett-Ghorayeb. “However, there is still much to explore.”
Source: www.nbcnews.com
