The gravitational acceleration of a planet is proportional to the planet's mass, and inversely proportional to square of the planet's radius.
So when you stand on the surface of this particular planet, you feel a force of gravity that is
(1/2) / (3²)
of the force that you feel on the surface of the Earth.
That's (1/18) as much as on Earth.
The acceleration of gravity there would be about 0.545 m/s².
This is about 12% less than the gravity on Pluto.
