Mercury: The planet with a spider

The only reason we have mountains is because the Earth is shrinking, causing its surface to buckle up into peaks. At least that’s what people believed 200 years ago. Nowadays we know that it’s all down to tectonic activity on Earth, but somewhere else in our Solar System, shrinking may actually be the reason for mountains. The planet: Mercury.

New images released by NASA following the flyby of Mercury by their Messenger probe in January have revealed strange new things about a planet that up until now was considered, well, boring.

So what caused Mercury to shrink, and then create these huge mountain chains? It’s all down to the fact that Mercury’s interior cooled after its formation; when things cool, they contract. Because Mercury has not had any tectonic activity (volcanoes, earthquakes) for billions of years, the effects of that contraction can still be seen today.

Also revealed in the new photos was a strange feature, dubbed ‘The Spider’ (see image on right). It is thought to be the remnants of an ancient volcano, though there is also a meteorite crater near the peak.

–

–

Another revelation was that Mercury’s not so bland and colorless after all – faint blue and red/pink tinges have been detected by Messenger’s cameras (see image at top).

Messenger makes another flyby in October this year, then again in 2009, before finally coming into orbit around the Solar System’s smallest planet in March 2011. I think we can expect plenty more fascinating news from Messenger over the next few years.

See my previous posts about the Messenger missions to Mercury here and here.

What’s so great about Mercury? Quite a bit, actually.

What’s so great about Mercury? Isn’t it a bit boring, with no rings (like Saturn has), no giant storms the size of Earth (as on Jupiter), and in fact nothing but loads and loads of craters?

Even if doesn’t seem particularly special, Mercury still looks beautiful, and it can tell us a great deal about the history of our own planet.

NASA’s Messenger probe, the first one to visit in over 30 years, has taken some stunning shots, a few of which are posted below. Click to enlarge.

For more information, NPR’s Science Friday had a fascinating interview with a scientist working on the project, which can be downloaded here (about 20 minutes long)

Messenger actually got just 125 km from Mercury’s surface, enabling it to get detailed pictures of the craters that cover this rocky planet. One crater, the Caloris basin, is among the biggest in the Solar System.

 –

 –

 –

 –

–

 –

–

 Why so many craters?

The other planets have been bombarded almost as much as Mercury during their 4.5 billion year history, but because Mercury has no wind, water or volcanic activity to erode the craters away, it’s far more cratered than the other planets. Looking at Mercury’s craters can tell us what our Earth used to be like.

Some scientists suggest Mercury may have been bombarded more than other planets, because there would have been more asteroids the closer you got to the Sun.

 –

–

Why no color?

All the other planets either have colored elements in their rocks – like Mars, which contains large amounts of iron – or they have an atmosphere – think of Jupiter and Saturn. This leaves Mercury looking much like our Moon.

Going to Mercury

With temperatures ranging from 801 to -279 degrees F (that’s 427 to -173 degrees C), Mercury isn’t really the sort of place you’d want to go on vacation. But hostile though it may be, you would think we’d still have done loads of exploration there with spacecraft… Well actually, it has not been visited since 1975, so when NASA’s Messenger probe makes its first flyby on Monday January 14 2008, we should be seeing a new dawn in the exploration of this strange planet. Considering the technological advances we’ve made in the last 30 years, the results of this probe should be very exciting.This mission raises an interesting question: is it right to send loads of missions to Mars just because that is the first new planet humans are most likely to step foot on, while largely neglecting the other planets (with the exception of Saturn), where important scientific discoveries could be made? Leave your opinion in the comments below.