Flares Challenge Habitability of Bodies beyond Earth

Flares Challenge Habitability of Bodies beyond Earth

In my previous blog post, “Bad Flare Days,” I discussed the latest research establishing how blessed we are to be orbiting a star with the least number of bad flare days, where even on its “bad” days, it is not so bad. As I explained, it is not so bad because our Creator placed us on Earth at the one precise moment in the Sun’s history when its flaring activity is at rock bottom.

In this blog post I will explain why, in spite of the Sun exhibiting such an extremely low level of flaring activity, any possible life on solar system bodies besides Earth is limited (at best) to extremely radiation-resistant or subsurface microbes. I will also explain why stellar flares seriously challenge the possible habitability of extrasolar planets and moons.

Bad Flare Days for Other Solar System Bodies
Mars: Ultraviolet and particle radiation from solar flares compared to the flux on Earth is a factor of two lower for Mars and a factor of two higher for Venus. Present-day Mars, however, has a highly rarefied atmosphere and a negligible magnetic field. Thus, unlike Earth, Mars lacks preventive radiation shields. The flux of ultraviolet and particle radiation from solar flares on Mars’s surface will be at least a hundred times greater than the flux on Earth’s surface.1 Therefore, solar superflares will prove fatal to any life on Mars with the possible exception of extremely radiation resistant bacteria akin to Deinococcus radiodurans.2

Venus: For Venus, the role of surface radiation is irrelevant since Venus’s surface temperature of 462° Centigrade (863° Fahrenheit) is much too hot to sustain any form of physical life. High up in the clouds of Venus the temperature is much cooler. Venus’s clouds, however, contain a high concentration of sulfuric acid. Nevertheless, some researchers have speculated that sulfur-based chemoautotrophic bacteria might survive in Venus’s upper atmosphere.3 Venus’s lack of a magnetic field, its proximity to the Sun, and the more rarefied nature of its upper atmosphere imply that solar superflares would subject any possible life in its upper atmosphere to catastrophic extinction events.4

Moons of Jupiter and Saturn: Astronomers have speculated that the water content and chemistry of Jupiter’s moon, Europa, and Saturn’s moons, Enceladus and Titan, might make them candidates for harboring life. Though these bodies are much more distant from the Sun than Earth, their lack of radiation shields means that solar superflares would render physical life impossible on their surfaces. Microbes many miles below the surfaces of these moons, though, could be adequately shielded from solar superflare radiation. However, no conceivable chemistry would permit the origin of life at such depths.5

Bad Flare Days for Extrasolar Bodies
About 85 percent of all still-burning stars are M- or K-type dwarf stars. These stars are smaller and much dimmer than the Sun. Their low luminosities imply that for their planets to possess liquid water, such planets must orbit their host stars at much smaller distances than Earth orbits the Sun. The close-in orbits expose these planets to much more intense ultraviolet and particle radiation from stellar flares. Furthermore, M- and K-type stars manifest dramatically more frequent and intense flares than G-type stars (the Sun is a G-type star).6

Astronomers have calculated that the greater flaring activity of M- and K-type stars and the closer proximity of any possible liquid-water-bearing planets orbiting them guarantee that the atmospheres of such planets would be completely stripped away in less than one billion years.7 Also, these planets will be fully or partially tidally locked. That means daytimes on these planets will exceed several months, they will possess weak or nonexistent magnetic fields, and their shielding against superflare radiation from their host stars will be feeble. The level of surface ultraviolet radiation due to flares will be lethal to all physical life-forms.

It is even doubtful that such planets will possess any surface liquid water. Two astronomers determined that for liquid-water-bearing planets orbiting M-type stars, superflares from these stars would completely desiccate (dry up) these planets in under 100 million years.8 Liquid-water-bearing planets orbiting K-type stars might keep their water for as long as a billion years.

Stars larger than the Sun, F-, A-, B-, and O-type stars, exhibit greater flaring and superflaring activity than G-type stars. They also burn up their nuclear fuel at much faster rates. Thus, liquid-water-bearing planets orbiting these bigger stars likewise will be desiccated in under one billion years.

Even G-type stars, the category to which the Sun belongs, are not immune from superflare catastrophes. As I described in my previous blog post, “Bad Flare Days,” the Sun has the lowest superflare rate of any known G-type star.

Harvard astronomers Manasvi Lingam and Abraham Loeb stated, “One may thus be tempted to conclude that complex life is rare in the universe.”9 Rare indeed. Based on superflaring data and many other factors, one may be drawn to conclude that the Sun and Earth are uniquely and supernaturally designed by a personal intelligent Creator to make possible a home for us human beings.

Featured image: Solar Flare on October 2, 2014. This flare is about one-tenth as powerful as the most powerful flares in the past two centuries of the Sun’s history.
Image credit: NASA/Solar Dynamics Observatory

  1. Manasvi Lingam and Abraham Loeb, “Risks for Life on Habitable Planets from Superflares of Their Host Stars,” Astrophysical Journal 848 (October 10, 2017): id. 41, doi:10.3847/1538-4357/aa8e96; J.-M. Grießmeier et al., “Galactic Cosmic Rays on Extrasolar Earth-Like Planets I. Cosmic Ray Flux,” Astronomy & Astrophysics 581 (September 2015): id. A44, doi:10.1051/0004-6361/201425451.
  2. Michael M. Cox and John R. Battista, “Deinococcus radiodurans—the Consummate Survivor,” Nature Reviews Microbiology 3 (November 1, 2005): 882–92, doi:10.1038/nrmicro1264.
  3. Dirk Schulze-Makuch et al., “A Sulfur-Based Survival Strategy for Putative Phototrophic Life in the Venusian Atmosphere,” Astrobiology 4 (July 5, 2004): 11–18, doi:10.1089/153110704773600203.
  4. Lingam and Loeb, “Risks for Life,” 7.
  5. Fazale Rana and Hugh Ross, Origins of Life: Biblical and Evolutionary Models Face Off (Covina, CA: RTB Press, 2014), 205.
  6. Allison Youngblood et al., “The MUSCLES Treasury Survey. IV. Scaling Relations for Ultraviolet, Ca II K, and Energetic Particle Fluxes from M Dwarfs.” Astrophysical Journal 843 (June 28, 2017): id. 31, doi:10.3847/1538-4357/aa76dd; John Scalo et al., “M Stars as Targets for Terrestrial Exoplanet Searches and Biosignature Detection,” Astrobiology 7 (April 11, 2007): 85–166, doi:10.1089/ast.2006.0125; Hugh Ross, “Inhabitability of Planets Orbiting Red Dwarfs,” Today’s New Reason to Believe (blog), Reasons to Believe, July 30, 2017, https://www.reasons.org/todays-new-reason-to-believe/read/todays-new-reason-to-believe/2017/07/30/inhabitability-of-planets-orbiting-red-dwarfs.
  7. Manasvi Lingam and Abraham Loeb, “Physical Constraints on the Likelihood of Life on Exoplanets,” International Journal of Astrobiology, published online July 6, 2017, doi:10.1017/S1473550417000179; Chuanfei Dong et al., “The Dehydration of Water Worlds Via Atmospheric Losses,” Astrophysical Journal Letters 847 (September 14, 2017): id. L4, doi:10.3847/2041-8213/aa8a60; K. Garcia-Sage et al., “On the Magnetic Protection of the Atmosphere of Proxima Centauri b,” Astrophysical Journal Letters 844 (July 24, 2017): id. L13, doi:10.3847/2041-8213/aa7eca; Chuanfei Dong et al., “Is Proxima Centauri b Habitable? A Study of Atmospheric Loss,” Astrophysical Journal Letters 837 (March 10, 2017): id. L26, doi:10.3847/2041-8213/aa6438.
  8. Lingam and Loeb, “Risks for Life,” 8.
  9. Lingam and Loeb, “Risks for Life,” 8.