# Jump on a comet

Is it possible to stand, walk or jump on a comet?

How to stand on a comet?

Gravity is a force that attracts all objects downwards, or more precisely, towards the centre of the mass. For a planet, this centre of mass coincides with the centre of the planetary sphere, but for non-spherical bodies of mass like 67P/Churyumov Gerasimenko, its centre of mass is a little more complicated to determine and the gravitational field is subject to high variations depending on the area measured.  Not only is gravity very weak (between 10,000 and 100,000 times weaker than on Earth), but it would also be difficult to keep your balance vertically!

If an astronaut was standing on 67P, he would not be able to stand straight (perpendicular) in respect to the ground.

How to walk on a comet?

If what we just learned, that standing straight doesn't mean being perpendicular to the ground, then you would understand that walking on a comet would be challenging.  If somehow you still manage to overcome this challenge, it would be important to walk slowly and lightly. Don't even think about jumping or running, you risk sending yourself into orbit!

Can we jump up in the air (in space!) on a comet?

Unless there's elastics holding you to the ground, dream on! The attraction of the gravitational force is about 10 m/son Earth but varies between 0.0001 and 0.001 on the comet 67P.  This intensity of the gravitational field on the surface of a celestial body makes it possible to determine the escape velocity (or rate of release). It's the velocity required for an object to separate itself from the attraction of the celestial body. The escape velocity of Earth is 11 km/s (40,000 km/h). That's why such powerful rockets are needed to attain such speeds. On 67P/Churyumov Gerasimenko, the escape velocity is about 1 m/s (3.5 km/h). That speed is easily attainable by human strength and one good jump is all that's needed to send you into space for a very, very long time.

For these reasons, and many more, we can confirm that no astronaut will land on such a small comet. It's also for these reasons that the Philae lander has harpoons to anchor itself to the comet while landing and avoid bouncing off.