John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
NASA says it's a “once-in-a-lifetime event.”
Finland and Norway better watch out, because there's a new player in the northern-lights game. That would be Mars, which due to a brush-up with a comet could shimmer with ghostly, extraterrestrial auroras this Sunday.
Comet Siding Spring is flying in from the lovely Oort Cloud and will miss Mars by a relative hair (82,000 miles, about one-third the distance from Earth to the Moon). The dual bodies are likely to have an interaction—Mars is shrouded with CO2, and comets can travel with dusty comas wider than Jupiter. Says the appropriately named David Brain at the University of Colorado: "We hope to witness two atmospheres colliding."
What might that look like? The above NASA video gives one guess and it is... rainbow lesions. Unlike earth's robust magnetic field, Mars is dotted with a "patchwork of magnetic umbrellas." Behold, the planet's magnetosphere, looking like a weirdly cute virus:
Any possible auroras will appear in the upper regions of these bulges:
Because an advanced spacecraft called MAVEN recently reached Mars, the NASA folks will have an excellent view of any aurora activity. Well, perhaps it could be a little better considering the space agency has moved all its probes to the opposite side of the planet so they don't get hole-punched by the comet's whizzing dust particles. "We're going to hide behind Mars," explains one scientist. "So, kind of like diving under your desk if there's an earthquake and flying glass around.... We're not going to take any chances."
Though NASA calls this cosmic confrontation a "once-in-a-lifetime event," it's not the first time a planet other than Earth has glowed with strange lights. Here's Jupiter's version of the aurora borealis, captured more than a decade ago by the Hubble Space Telescope: