Astronomers have made an intriguing discovery of a planet called LP 791-18d, which is unlike Earth in many ways. This Earth-sized planet orbits a small red dwarf star approximately 90 light years away. What makes this planet particularly fascinating is its unique characteristics: half of its surface is perpetually bathed in daylight, while the other half remains in eternal darkness, creating a striking contrast. Additionally, LP 791-18d is covered in a vast expanse of active volcanoes, further piquing the interest of scientists.
The significance of volcanism lies in its ability to facilitate interaction between a planet’s interior and exterior, making it an essential process for the development of a planetary atmosphere. With the presence of an atmosphere, there is a possibility of surface liquid water, which is a crucial requirement for supporting life as we currently understand it, explains Stephen Kane, an astrophysicist from UC Riverside.
Prior to the discovery of LP 791-18d, astronomers were already aware of two other planets in this star system, namely LP 791-18b and c. Planet c, which is about 2.5 times the size of Earth and nearly nine times its mass, orbits the star in close proximity to planet d. As the two planets pass near each other during their orbits, the massive size of planet c exerts a gravitational pull on planet d, causing its orbit to become elliptical rather than perfectly circular. These orbital deformations generate friction, resulting in the heating of LP 791-18d’s interior and the subsequent volcanic activity observed on its surface.
The discovery of LP 791-18d was made possible through data gathered by NASA’s Transiting Exoplanet Survey Satellite (TESS) and the retired Spitzer Space Telescope. Stephen Kane, who was involved in the original TESS observations, co-authored a paper on this newfound planet published in the scientific journal Nature.
Another intriguing characteristic of LP 791-18d, as detailed in the research paper, is its lack of rotation. The planet is tidally locked to its star, meaning that one side perpetually faces the star while the other remains in constant darkness. The side facing the star would likely be too hot for liquid water to exist, but the paper suggests that the extensive volcanic activity occurring across the planet could sustain an atmosphere. This atmospheric presence may allow water to condense on the night side of LP 791-18d.
While the abundance of constantly erupting volcanoes would render the planet inhospitable to life as we know it, their existence provides valuable insights into the processes of evolution. Jessie Christiansen, a co-author of the paper and a research scientist at the California Institute of Technology, highlights the question of whether tectonic or volcanic activity is necessary for life, which remains a significant topic in the field of astrobiology. In addition to potentially creating an atmosphere, these volcanic processes could stir up materials that would otherwise sink and become trapped in the planet’s crust, including carbon, a vital element for life.
The recent discovery of active volcanoes on Venus has also shed light on the fact that Earth-sized planets can continue to accumulate an atmosphere, even without plate tectonics. Volcanic emissions primarily consist of carbon dioxide and water vapor, which are greenhouse gases capable of trapping heat and maintaining a planet’s warmth. Stephen Kane mentions the example of Venus, where volcanic carbon dioxide contributed to a runaway greenhouse effect, resulting in scorching surface temperatures exceeding 850 degrees Fahrenheit. Although the likelihood of life existing on present-day Venus is slim, the study of volcanoes on planets like LP 791-18d can provide valuable insights into how volcanic activity shapes planetary environments over time, including those of Venus and Earth.