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Yahoo
21-05-2025
- Science
- Yahoo
Lightning on alien worlds may fail to spark life, simulations suggest
When you buy through links on our articles, Future and its syndication partners may earn a commission. Life as we know it may require lightning, as it's one of the few energy sources a planet has available to create complex chemical compounds. Now, new research has found that lightning, while not very common, can occur on tidally locked exoplanets like our nearest neighbor, Proxima b. But the peculiar nature of lightning on tidally locked planets poses some challenges for their ability to host life. A typical lightning bolt can reach temperatures of up to 30,000 kelvins (over 50,000 degrees Fahrenheit). That's more than powerful enough to destroy common atmospheric gases and reassemble them into new compounds. On modern-day Earth, lightning breaks down molecular nitrogen and oxygen and creates nitrogen oxides. On the early Earth, however — before the rise in atmospheric oxygen due to photosynthesis — lightning may have played a crucial role in creating many prebiotic compounds, which are molecules that form the building blocks of proteins. We don't know if any exoplanets host life. We have yet to find an Earth twin with the right orbit around a sun-like star, but we have come close. Take Proxima b, an exoplanet that orbits the nearest star to the solar system. Proxima b is roughly the size of Earth and orbits its star, Proxima Centauri, at just the right distance to potentially support liquid water. But Proxima Centauri is a red dwarf star, with just a fraction of the sun's brightness and size. Proxima b has an incredibly tight orbit, with an entire year lasting just 11 days. Because of its proximity to its parent star, Proxima b is almost certainly tidally locked, meaning it always shows one face toward the star, just like the moon always shows only one face toward Earth. Because of its rotation, our planet hosts a rich weather system. This weather system makes lightning storms very common, with roughly 100 lightning strikes happening somewhere on the globe every second. But can a tidally locked planet create lightning storms? To answer this question, a team of researchers led by Denis Sergeev at the University of Bristol in the U.K. created atmospheric simulations of a mock tidally locked planet, using the same kinds of simulations that climatologists use to study Earth's weather. In April, they submitted their paper for publication in the journal Monthly Notices of the Royal Astronomical Society. The researchers found that the tidally locked planet could produce significant lightning storms, but that these storms were far different from those on Earth. These planets around small stars hosted significantly fewer lightning strikes — only a handful of strikes per second, the simulations showed. And that was for planets with much thinner atmospheres than Earth's atmosphere — roughly a quarter of our planet's atmospheric pressure. Higher-pressure atmospheres suppressed the formation of convection cells that could drive cloud formation and generate the necessary friction to produce lightning. Atmospheres with pressures 10 times greater than Earth's could produce only a single lightning strike every few minutes. Unlike on Earth, all the heat from the star pours onto one side on a tidally locked planet. That heat then flows through powerful jet streams that race from the permanent dayside to the nightside. This powered strong weather mostly on the dayside, with lightning strikes clustered in a circular area, the researchers found. However, in some cases, lightning strikes happened mostly on the nightside, just past the day-night terminator line. It was only there that there was enough atmospheric activity to generate the conditions needed for lightning. Related stories: —How could life survive on tidally locked planets? —Was life on Earth sparked by cloud-to-ground lightning strikes? —The 10 most Earth-like exoplanets But that doesn't mean that this lightning could necessarily be guaranteed to help produce life. For one, lightning strikes are far less common there than on Earth and thus may not be enough to generate sufficient prebiotic compounds. Another challenge is that the strikes are not distributed evenly around the globe. They tend to be concentrated on the dayside, which may be too hot to support life. Still, the story of life on exoplanets, even tidally locked ones, is not over. And nature has shown time and time again that life … finds a way.
Yahoo
19-05-2025
- Science
- Yahoo
TRAPPIST-1 Planets Could Be Swimming in Water, Study Shows
A seven-planet system some 40 light-years from Earth could be swimming in water, new research shows. In February 2017 scientists announced the discovery of several exoplanets orbiting the red dwarf star TRAPPIST-1, and ever since astronomers have keenly monitored the system for potential signs of life (aka biosignatures). According to recent findings, these planets may have an abundance of one of the most crucial elements for life: water. Since the discovery, scientists have gone back and forth on whether any planets in the TRAPPIST-1 system could be habitable. Much like the Proxima Centauri system and its Earth-like planet (Proxima b), the debate has centered on their parent stars: M-type (red dwarf) stars. These stars are smaller and cooler than our Sun and are noted for the way they are prone to flare activity. Another major question is the availability of water in this system. Previous findings have indicated that planets orbiting red dwarfs may have an overabundance of water, but they may not hold onto it for long. These findings are supported by other research that has revealed that these planets experience high rates of water lost to space, caused by the intense ultraviolet (UV) radiation from their host star. In a new study, a team of researchers led by astrobiologist Trent Thomas from the University of Washington addressed recent findings by the JWST. Recent observations by JWST of TRAPPIST-1 c ruled out a thick carbon dioxide atmosphere, indicating that the planet is not as "Venus-like" as previously thought. However, these observations did not rule out the presence of water vapor or oxygen produced by its chemical dissociation. As the team explained in their paper, "the maintenance of atmospheric water vapor would require a present-day water source, such as volcanic outgassing." To investigate this possibility and estimate plausible outgassing rates on the TRAPPIST-1 planets, the team developed a theoretical outgassing model based on the rocky planets of the Solar System ( Mercury, Venus, Earth, and Mars). They then applied filters based on observations of the system and what is known about its geochemistry to constrain plausible scenarios. Their findings indicated that the outgassing rates of all seven planets would be between 0.03 and eight times that of Earth. However, they also found that magma emplacement rates (the speed at which magma moves through a planet) were similar to those of Mars. While there are indications that Mars still has magma beneath its surface, it is considered 'volcanically dead'. The same may be true of the TRAPPIST-1 planets. "Our model results for magma emplacement rates also indicate that the TRAPPIST-1 planets are currently more likely to have low-to-no volcanic activity," the researchers write in their paper. "Our results indicate that the water outgassing rates on the TRAPPIST-1 planets are more likely to be lower than Earth's, but the plausible range also includes outgassing rates that are an order of magnitude higher than Earth's." Their results further indicated that the TRAPPIST-1 planets may have relatively dry Earth-like mantles. But as they emphasized, it is possible that water could make up to 1 percent of their mass fractions. "Our results indicate that drier mantles are preferred within the broader explored range of mantle water content," the team explains. "This arises due to our assumption that the TRAPPIST-1 planets have terrestrial interiors with mantle water contents that remain below 1 percent by weight upper limit throughout the 5.4 billion-year age of the TRAPPIST-1 system. The preference for lower mantle H2O values is more consistent with Earth's mantle water content." This is especially interesting considering that while water covers about 71 percent of Earth's surface, it constitutes only about 0.02 percent of its total mass. This could mean that planets orbiting within TRAPPIST-1's habitable zone are volcanically inactive and have varying degrees of water, ranging from potential 'water worlds' and barren rocky worlds to Earth-like planets covered in oceans. These results reinforce the idea that the TRAPPIST-1 system has no shortage of water. Unfortunately, many questions remain about its habitability. Fortunately, Webb's observations of TRAPPIST-1 (and other red dwarf systems) are still in their infancy. Additional observations will allow astronomers to constrain the potential habitability of this system. Their findings were reported in a preprint available on arXiv. Unknown Species of Bacteria Discovered in China's Space Station NASA Mission Captures Eerie New View of The Moon And Sun Mysteriously Perfect Sphere Spotted in Space by Astronomers
