Not every moon is a moon, most are captured objects

Showing all posts about Pluto

Not every moon is a moon, most are captured objects

9 January 2014

Here’s a 2010 photo, taken by the European Space Agency’s Mars Express probe, of Phobos, one of two… moons orbiting Mars. But that’s not a moon. And nor is Deimos, Mars’ second so-called moon. In reality they’re merely random rocks captured by the Red Planet at some point in the past.

Take a look at Earth’s moon. The Moon. It’s elegant, sizeable, and spherical. The same cannot be said of the rocks orbiting Mars, a couple of unfortunate asteroids that once strayed a tad too close to the fourth planet. Most of the outer planets of the solar system have moons similar in stature to Earth’s satellite, but they also host a bunch of minuscule, oddly shaped rocks, called moons simply because they orbit the planet in question.

It makes me think it is time to consider what really constitutes a moon. If Pluto can no longer be regarded as a planet, why then must every last rock that has been pulled into orbit by a planet, be called a moon? Surely such bodies should adhere — like planets, real planets — to some sort of criteria before being called a moon.

Being pretty much spherical, and of a certain size and mass, could form basic benchmarks, and anything under a certain size should be referred to as a captured object rather than a moon. Sorry Mars, but both your orbiting companions, Phobos and Deimos, are captured objects, not moons.

Originally published on Thursday 9 January 2014.

Pioneers 10 and 11 courses inexplicably varying at Kuiper Belt

15 September 2004

Something weird is happening out on the boundary of our solar system, an area called the Kuiper Belt, where NASA space probes Pioneers 10 and 11 are presently located.

Both deep space probes, launched over thirty years ago, traversed the inner region of the solar system almost exactly according to plan.

Since passing beyond the orbit of Pluto though, events have taken an unexpected turn: both probes appear to be inexplicably deviating from their projected courses.

And no one can work out why. Some scientists think long held ideas on the effects of gravity over extended distances may be need to be re-thought. Others say that both probes may be leaking gases, which is contributing to the change in their trajectories.

This mystery has led to calls for a new deep space mission to see what’s happening out at the Kuiper.

By fitting a Pioneer follow-up probe with new measuring equipment, navigational device and communications gear, it should be possible to discover if the probes are in the grip of a new force of nature.

A new force of nature? Perhaps Star Wars director George Lucas’ far, far, away galaxy may not be all that distant after all…

Originally published Wednesday 15 September 2004.