And our rovers will be there to watch the whole thing.

This weekend, a rare and ancient comet is going to fly extremely close to Mars, and it's predicted to put on quite a show.

In fact, it'll pass Mars at a distance of 139,500 kilometres - just one third of the distance from here to the Moon. That's much, much closer then any comet has ever flown by Earth, that we know of.

The comet's being called the Siding Spring Comet, after the Australian observatory from where it was detected, and it's a long way from home - it's already spent millions of years travelling from the Oort cloud, a mass of icy comets that hangs frozen at the furthest reaches of our Solar System, at a mind-blowing speed of around 56 kilometres a second.

These Oort cloud comets are extremely rare, and astronomers are keen to find out more about them. Luckily, our Mars rovers and orbiters will be watching the fly-by closely - along with the Hubble Space Telescope and hundreds of other instruments on Earth.

As NASA explained in a press release:

Comets from the Oort cloud are both ancient and rare. Since this is Comet Siding Spring's first trip through the inner solar system, scientists are excited to learn more about its composition and the effects of its gas and dust on the Mars upper atmosphere. NASA will be watching closely before, during, and after the flyby with its entire fleet of Mars orbiters and rovers, along with the Hubble Space Telescope and dozens of instruments on Earth. The encounter is certain to teach us more about Oort cloud comets, the Martian atmosphere, and the solar system's earliest ingredients.

There's no danger to Curiosity on the surface of Mars as the rover is protected by the planet's thin atmosphere. However, there's the small chance that the dust and debris from the comet's tail will damage the spacecraft orbiting Mars, such as Maven and India's Mangalyaan. NASA is now "taking steps to protect is Mars orbiters, while preserving opportunities to gather valuable scientific data". This all goes down around 2.27pm New York Time, or 5.27am on Monday in Australia.

Fingers crossed for our robot explorers out there, we'll be thinking of you guys.

Watch the narrated NASA video below to see a simulation of how the fly-by will look from Mars:

Find out more about the comet over at NASA.

Source: Sploid, NASA