A comet near Mars may strike it in a powerful impact, potentially making the planet much warmer. The Red Planet is luring many entrepreneurs, including billionaire Dennis Tito, who aims to beat other nations by sending a man and a woman to Mars.

The make-or-break window for this possible game-changer is October 2014. At that time, an Oort cloud comet called C/2013 A1, first discovered last month, will approach Mars, missing it by about 35,000 km, which is quite close.

However the comet’s trajectory is still uncertain, which leaves a small chance it could impact the planet, said Russian astronomer Leonid Elenin, who worked on calculating the course of the celestial body. The comet will be travelling at a speed of 56 kilometers per second relative to Mars when it passes; if they do collide, the resulting explosion would be equal to a 20,000-gigaton bomb blast – powerful enough to leave a 50-kilometer crater on the planetary surface

The event would trigger a major change of the Martian climate, Australian space scientist Robert Matson explained. The impact would evaporate large amounts of water and carbon dioxide ice from the comet, spread across a planetary scale, making the climate on Mars much warmer due to the greenhouse effect.

On the other hand, the blast would also raise huge clouds of dust and could trigger volcanic activity in the mostly-inert planet. Both would make more sunlight bounce off the Martian atmosphere, which would make the planet colder. A heating effect is likely to prevail, however.

But such dramatic change is far from certain, with more observation needed to narrow down the comet’s trajectory. Even if it is a simple close flyby, it will still be a rare chance to take high-resolution pictures of the object with the Mars Reconnaissance Orbiter mission.

The rush to Mars

Private space companies are now challenging nations not only for Low Earth Orbit deliveries but also for reaching outer space. Last week, billionaire and private space explorer Dennis Tito launched the non-commercial Inspiration Mars Foundation, which hopes to send a manned mission to flyby Mars in 2018.

The crew of the capsule could be a married couple yet to be selected, Tito announced on Wednesday, who would have to not only cope with the difficulties of a Spartan and low-gravity ship environment, but also with spending just over 500 days confined together in an enclosed space.

The mission plans to use a modified SpaceX Dragon capsule with an inflatable living module attached. It will be mostly carried by gravity on its way to Mars and back home, with little help from the rocket engines, a maneuver known as a ‘free return’ trajectory. The same approach was used for NASA’s Apollo missions to the Moon.

The Tito-funded spacecraft would pass Mars at the distance of around 160 kilometers at its closest point. The return landing on Earth would be at a record-high speed of 14.2 kilometers per second, which would require a special and highly resilient heat shield.

More traditional players in the space arena are also eyeing Mars as the next frontier. NASA and ESA have a well-established presence around and on Mars. And this week, India confirmed that it is within the timeframe to launch its Mangalyaan mission to Mars in November 2013.

Russia plans to land a rover on Mars in 2018, hopefully rehabilitating its space program after the embarrassing failure of its Phobos-Grunt survey mission. There is also collaboration between Finnish, Russian and Spanish participants on a plan to deliver several dozen landers to Mars to form a meteorological observation network on its surface.