Lightning on Saturn captured by NASA’s Cassini spacecraft in 2009. Credit: NASA/JPL-Caltech/SSI
Earth has weather–we see it, feel it, and sense it with technology. Our solar system neighbors have weather, too. Venus has dramatic sulfuric acid rainstorms. Mars has dry windstorms. And it turns out: a couple of these weather phenomena might provide key components in creating and sustaining life.
The spectacular light show we see during thunderstorms here on Earth aren’t exclusive to our planet. Both gas giant planets like Jupiter and brown dwarfs also have clouds in their atmospheres capable of conducting electricity. When oppositely charged particles in the atmosphere create an electric field, free electrons careen to the positively charged side of the field. This electric field can be created in water clouds, volcanic ash clouds, and even in brown dwarf gemstone clouds (glittery clouds made of silicates and metals in the atmosphere of a brown dwarf that condensed into dust particles). When these free electrons collide in massive quantities, lightning strikes.
And where there’s lighting, there could be life.
Lightning in the eye of Tropical Cyclone Bansi seen from the International Space Station Jan. 17, 2015. Credit: NASA
In 1953, scientists Stanley Miller and Harold Urey pulled off a now infamous experiment suggesting how the electric crackling of a lightning strike could have provided the high energy necessary to forge complex organic compounds from simple molecules in Earth’s ancient atmosphere. These compounds, amino acids, are called the “building blocks of life” because they link together to create the proteins that play a key role in performing our genetic code. While scientists now believe that Earth’s primordial soup requires a very precise recipe, lightning may be the key ingredient needed to jolt life into existence from this nutrient-rich broth.
Diagram of the Miller-Urey Experiment.
Another phenomenon called an aurora is created when charged particles interact with a magnetic field. Auroras, like those on Earth and Jupiter, are useful indicators of the strength of the planet’s magnetic field. The stronger the magnetic field, the more protection the planet has from harmful incoming solar radiation. Our mighty magnetic field on Earth is partly accountable for the success of life here, so looking for strong auroras on other worlds may tell us about their habitability potential.
This is one of a series of night time images photographed by one of the Expedition 29 crew members from the International Space Station. It features Aurora Australis, seen from a point over the southeast Tasman Sea near southern New Zealand. Credit: NASA
Auroras may also be useful for finding life on other planets in another way–by pointing us to new exoplanets. Since exoplanets are so faint, astronomers are always looking for new ways to detect them besides direct imaging. One indirect method that has gained attention is by looking for auroras on brown dwarfs. Here’s how:
In 2015, astronomers discovered radio wave bursts emitting from brown dwarf LSR J1835+3259. These radio waves signaled that charged particles were entering the brown dwarf’s atmosphere and interacting with its magnetic field to create an aurora. But since the brown dwarf wasn’t orbiting a star, astronomers were puzzled by the particles’ origins. Perhaps, they explained, if an exoplanet was in orbit around the brown dwarf, it could interrupt the brown dwarf’s magnetic field and trigger auroras, much in the same way that Jupiter’s moon, Io, triggers auroras on Jupiter.
Astronomers are using NASA’s Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the solar system, Jupiter. Credits: NASA, ESA, and J. Nichols (University of Leicester)
Gregg Hallinan, an astronomer at the California Institute of Technology, believes it’s possible that nearly 10% of brown dwarfs have these strong magnetic interactions happening. It‘s possible that some, many, or all of these brown dwarfs with magnetic interactions have exoplanets in orbit causing the disruption.
Astronomers now know that not only are lightning and auroras found elsewhere in the solar system, but that these phenomena can indicate potential life on other planets. All astronomers have to do is look for them. But looking isn’t always so easy–these phenomena which are brilliantly bright to us are rather dim when peering far out into space. In the next decade, extremely large and high-precision telescopes will be built to look specifically at the atmospheres of exoplanets, and may even be able to see the colors of auroral light shows. Until then, astronomers search in indirect ways, such as using auroras as exoplanet markers around brown dwarfs. What astronomers have learned from these luminous discoveries is that weather phenomena can shape a planet as drastically as a planet’s make-up can shape its weather.