Comet Siding Spring

Video credit - NASA/JPL

On Sunday, a comet is going to fly past Mars, so close that for a time, scientists wondered if it would hit the planet.

Should I repeat that?

On Sunday, a comet is going to fly past Mars, so close that for a time, scientists wondered if it would hit the planet.

This comet, named "Siding Spring" after the observatory where it was first detected, will get within 87,000 miles of the surface of Mars (three times closer than the Moon is to Earth). NASA has moved its orbiting satellites to the far side of Mars to shield them from the comet's tail of debris. On the surface, our rovers should be safe, thanks to Mars' atmosphere.

Presuming all goes well, all these instruments should be able to help us study this amazing comet. Comet Siding Spring comes from the Oort Cloud, which is a mess of ancient ice and rock at the edge of our solar system. This is the first time Comet Siding Spring is coming past the outer planets towards the Sun, so it is relatively intact (never been too close to heat), the same as it would've been during our solar system's formation 4.6 billion years ago.

Image credit: NASA.

For Comet Siding Spring, this is a one way trip. But for us, it's the journey of a lifetime. Thousands of lifetimes. In fact, the odds of a comet sailing by Mars is about once per millennia, if that.

If this had happened 50 or more years ago, we wouldn't have been able to study it.

If it had happened 40 years ago, we may have had one-ish orbiter in place, but next to no control to move that orbiter to a safe viewing spot.

Heck, if it had happened one month ago, we would have had only three orbiting satellites.

But it's happening NOW. We currently have five orbiting satellites. Plus two operational rovers on the planet itself.

This is going to be a spectacular chance to study an object from early in our solar system's formation, to better understand comets themselves (which have always been a tad mysterious to us), and to see what happens to a planet when something like a 5 mile wide space rock sails by.

So stay safe, MAVEN! Stay safe, MOM! Stay safe, MRO! Stay safe, Odyssey! Stay safe, Mars Express! And stay safe, Curiosity, Opportunity, and yes, even you, Spirit. We're all wishing you the best of luck in observing this amazing event. Please don't get too badly pummeled by any associated debris.