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Lightning Sprites Are Out Of This World

By David Reneke

David Reneke brings news from the space and astronomy communities around the world.

A few decades ago, scientists discovered the existence of “sprites” some 80 km above the surface of the Earth. Offshoots of electric discharges caused by lightning storms, they’re a valuable window into the composition of our atmosphere.

Recent experiments run by researchers again at Tel Aviv University show that sprites are not a phenomenon specific to our planet. “Jupiter and Saturn experience lightning storms with flashes 1000 or more times more powerful than those on Earth,” says PhD student Daria Dubrovin and her colleagues from the University. Dubrovin has recreated these planetary atmospheres in the lab to study the presence of sprites in space.

The colour of these bursts of electricity indicate what kinds of molecules are present and may explain the presence of exotic compounds, while providing an insight into the conductivity of distant planets’ atmospheres. This research could lead to a new understanding of electrical and chemical processes on Jupiter, Saturn and Venus.

Though a little-known and studied phenomenon, these extremely short-lived, reddish electric discharges are quite common on Earth because they occur in the mesosphere, a layer of the atmosphere that is even too high to be reached by atmospheric balloons.

Lightning as a generator of organic molecules has long been credited for contributing to the “primordial soup” that, according to current theories, led to the emergence of life on Earth.

Researchers are keen to know more about the possibility of lightning on other planets, not only because it can influence the directionality of future space programs but because it is another clue that could indicate the presence of extraterrestrial life.

To test for the viability of extraterrestrial sprites, Dubrovin and her fellow researchers recreated the atmospheres of Jupiter, Saturn and Venus in small containers. A circuit that creates short but strong voltage pulses produced a discharge that mimics natural sprites.

The team’s predictions could convince scientists operating the Cassini spacecraft, which is now orbiting Saturn, to point their cameras in a new direction. As Dubrovin points out, there’s currently a huge lightning storm occurring on Saturn producing at least 100 rare lightning discharges per second.

If researchers are able to obtain an image of the higher-up sprites from the Cassini spacecraft, it would enable them to gain more information about the storm below.

We Owe It All to Comets
Comets have always fascinated us. A mysterious appearance in ancient times could symbolise flood, fire, disease and pestilence. Seen as a portent of disaster, they could even mean a sure failure in battle, at least for one side.

Now, researchers have justified our fascination – but in a more benign light. Comets, it seems, might have played a very important and necessary part in the development of not only you and I, but every creature on this planet.

Comets are essentially large chunks of ice that formed in the early days of the solar system, far away from the Sun. The porous ice trapped the early gases and organic chemicals that were present in outer space.

The story started between 4.6 and 3.8 billion years ago, when these icy bodies slammed through the atmosphere, delivering a payload of organic materials to the young Earth that, combined with our own large reservoir of organics, eventually led to the emergence of life.

Curious about the connection, and while investigating their chemical makeup, Professor Akiva Bar-Nun of Tel Aviv University has formed a compelling case that comets were the source of missing ingredients needed to kickstart life in Earth’s ancient primordial soup.

Using a unique machine built at Tel Aviv University, researchers were able to simulate comet ice, and found that comets contain the ingredients necessary for providing the basic nutrients of life.

Specifically, researchers looked at the noble gases argon, krypton and xenon because they don’t interact with any other elements and are not destroyed by the Earth’s oxygen. These elements have maintained stable proportions in the Earth’s atmosphere throughout the lifetime of the planet, they report.

“The pattern of trapping of noble gases in the ice gives a certain ratio of argon to krypton to xenon, and this ratio, together with the ratio of gases that come from rocky bodies, gives us the ratio that we observe in the atmosphere of the Earth,” Bar-Nun said.

Carl Sagan wasn’t far wrong when he said we’re all made of star stuff!

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com