A NASA study suggests that 17 exoplanets may have life-supporting oceans under the ice, with potential geysers driven by internal heating. The study compared these exoplanets to Europa and Enceladus, intensifying the search for life in the universe.
A NASA study has expanded the search for life outside the solar system, suggesting that 17 exoplanets (worlds outside the solar system) may have oceans of liquid water, the basic building block of life, beneath their icy crusts. Water from these oceans occasionally erupts through the ice shell like a geyser. The scientific team calculated the amount of geyser activity on these exoplanets, and this is the first time these estimates have been made. They identified two exoplanets that were close enough to observe the signs of these eruptions with a telescope.
The search for life elsewhere in the universe is usually concentrated on exoplanets in the star's "habitable zone," at a distance where temperatures allow liquid water to persist on its surface. However, if an exoplanet that is too distant and too cold has enough internal heating, it is possible that it still has oceans under the ice shell. In our solar system, Jupiter's moon Europa and Saturn's moon Enceladus both have subterranean oceans because they are heated by tides caused by the gravitational pull of the host planet and neighboring moons.
These subsurface oceans can give birth to life if they have other necessities, such as energy** and the elements and compounds used in biomolecules. On Earth, entire ecosystems thrive in complete darkness on the ocean floor near hydrothermal vents, which provide energy and nutrients.
"Our analysis**, these 17 worlds may have ice-covered surfaces, but get enough internal heat from the decay of radioactive elements and tidal forces from the host star to sustain the inner oceans," said Dr. Lynnae Quick of NASA's Goddard Space Flight Center. "Because of the amount of internal heating they experience, all of the planets in our study may also exhibit low-temperature volcanic eruptions in the form of geyser-like plumes. Quick is the lead author of a recent article on the study published in the Journal of Astrophysics. In the course of their in-depth research, the team delved into the conditions of 17 confirmed exoplanets that are similar in size to Earth but less dense. This suggests that these planets may contain large amounts of ice and water rather than denser rocks. Although we don't know exactly what these planets are made of, preliminary estimates of their surface temperatures from previous studies have shown that they are much colder than Earth, which may mean that their surface is covered in ice. By using known surface brightness and Marinate.
2. Other characteristics such as Enceladus were used as models, and the surface temperature of each exoplanet was recalculated and optimized.
The team also used the morphology of the planets' orbits to calculate the heat generated by the tides and factor it into the expected heat of radioactive activity, thus estimating the total internal heat of these exoplanets.
Estimates of surface temperature versus total heat reveal the thickness of each exoplanet's ice – the ocean cools and solidifies at the surface while gaining heat from the inside. Eventually, they compared these data with Europa's data and used the estimated level of geyser activity on Europa as a conservative benchmark for exoplanetary geyser activity. Their ** surface temperature is 60 degrees Fahrenheit (about 33 degrees Celsius) lower than previous estimates. Estimates of ice crust thickness range from about 190 feet (58 m) in Proxima Centauri B and 1 mile (1) in LHS 1140 B6 km) to 2007 miles (24) of MOA 192LB6 km), while Europa estimates an average thickness of 18 miles (nearly 29 km). Estimated geyser activity from Kepler 441b to 17 per second6 lbs (about 8 kgs) to 639,640 lbs (290,000 kgs) for LHS 1140b and 13.2 million lb-s (6 million kgs) for Proxima B, compared to 4,400 lb-s (2,000 kgs) for Europa.
Because of our model**, oceans can be found relatively close to the surface of Proxima B and LHS 1140 B, and their geysers may be hundreds to thousands of times more active than Europa, so telescopes are most likely to detect geological activity on these planets," said Quick, who presented the study at the American Geophysical Union meeting in San Francisco on December 12. California.
This activity can be seen when exoplanets pass in front of their stars. Certain colors of starlight may be dimmed or blocked by the water vapor of the geyser. "Sporadic water vapor detections, in which the amount of water vapor detected varies over time, indicate the presence of a **mountain eruption," Quick said. Water may contain other elements and compounds that can reveal whether it can support life or not. Since elements and compounds absorb light in specific "signature" colors, the analysis of starlight will allow scientists to determine the composition of geysers and assess the habitable potential of exoplanets.
For planets like Proxima Centauri B, which do not pass through our star from our vantage point, geyser activity can be detected by powerful telescopes that are able to measure the light reflected by exoplanets as they orbit their stars. Geysers will expel icy particles on the surface of exoplanets, which will cause exoplanets to appear very bright and reflective.
Reference: Lynnae C quick、aki roberge、guadalupe tovar mendoza、elisa v.Quintana and Allison A"Prospects for the activity of the cold ocean planet ** mountain" by Youngblood, October 4, 2023, Journal of Astrophysics.
doi： 10.3847/1538-4357/ace9b6
The research was funded by NASA's Habitable World Program, the University of Washington's Astrobiology Program, and the Virtual Planetary Lab, a member of NASA's Scientific Coordination Group on Exoplanetary Systems.