Lightning Signature Could Help Reveal the Solar System's Origins

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Lightning Signature Could Help Reveal the Solar System's Origins
Karen C. Fox
NASA's Goddard Space Flight Center
May 3, 2012

Every second, lightning flashes some 50
times on Earth. Together these discharges coalesce and get stronger,
creating electromagnetic waves circling around Earth, to create a
beating pulse between the ground and the lower ionosphere, about 60
miles up in the atmosphere. This electromagnetic signature, known as
Schumann Resonance, had only been observed from Earth's surface until,
in 2011, scientists discovered they could also detect it using NASA's
Vector Electric Field Instrument (VEFI) aboard the U.S. Air Force's
Communications/Navigation Outage Forecast System (C/NOFS) satellite.

In a paper published on May 1 in The Astrophysical Journal, researchers
describe how this new technique could be used to study other planets in
the solar system as well, and even shed light on how the solar system
formed.

"The frequency of Schumann Resonance depends not only on the size of the
planet but on what kinds of atoms and molecules exist in the atmosphere
because they change the electrical conductivity," says Fernando Simoes,
the first author on this paper and a space scientist at NASA's Goddard
Space Flight Center in Greenbelt, Md. "So we could use this technique
remotely, say from about 600 miles above a planet's surface, to look at
how much water, methane and ammonia is there."

Water, methane and ammonia are collectively referred to as "volatiles"
and the fact that there are different amounts on different planets is a
tantalizing clue to the way the planets formed. Determining the
composition of a planet's atmosphere can be done with a handful of other
techniques - techniques that are quite accurate, but can only measure
specific regions. By looking at the Schumann Resonance, however, one can
get information about the global density of, say, water around the
entire planet. Simoes and his colleagues believe that combining this
technique with other instruments on a spacecraft's visit to a planet
could provide a more accurate inventory of the planet's atmosphere.

"And if we can get a better sense of the abundance of these kinds of
atoms in the outer planets," says Simoes, "We would know more about the
abundance in the original nebula from which the solar system evolved."

Accurate descriptions of planetary atmospheres might also help shed
light on how the evolution of the solar system left the outer planets
with a high percentage of volatiles, but not the inner planets.

Detecting Schumann Resonance from above still requires the instruments
to be fairly close to the planet, so this technique couldn't be used to
investigate from afar the atmospheres of planets outside our solar
system. Instead, scientists imagine something much more dramatic. After
a spacecraft is finished observing a planet, it could continue to detect
Schumann resonance as it begins its death dive into the atmosphere.
During the process of self-destruction, the spacecraft would still
provide valuable scientific data until the very last minute of its
existence.