Outer Space Down to Earth

Sunday , 7, June 2015

Next time you find yourself walking on a beach or at a river please be aware that you might bump into something quite spectacular, a shape or pattern formed by natural processes which can also be observed on other bodies in our Solar System. I present here two examples formed by flow.

The flowing landscape

The following image taken at a North Sea beach shows a beautiful pattern formed when the water level is receding, going towards ebb, and the sands soaked with water start to dehydrate causing little rivers to form seemingly out of nowhere. Please notice these teardrop shaped islands carved out by the water flow.

In outer space similar patterns can be observed. The image below shows a huge ancient channel system, now completely dried up, called Kasei Valles. It was carved out billions of years ago by – what most scientists agree on – catastrophic floods of water. The big round feature in the middle, an impact crater called Sharanov, is 100 kilometers across. Again take notice of the teardrop shaped islands, but now so much bigger in scale. What caused these massive outburst of water on Mars is still under debate.

Amazingly enough these catastrophic floods also took place on Earth. The image below shows a color map of the English channel sea bottom, south of the Isle of Wight. The grey areas are above sea level. The colors represent the sea bottom depth, which increases from red to orange, yellow, green, light blue to dark blue. The dark blue colors form a channel, now below sea level, and in the channel you can see in green again these teardrop shaped islands.

The channel was formed half a million years ago by a massive outburst of water following the collapse of an ice dam during a former ice age. The image, from left to right measures around 120 kilometers which makes this particular outflow a bit smaller than the Martian one, but still huge compared to what happens daily on our beaches.

Redrawn after Gupta et al. (2007)

Rounded by flow

When you walk on a rocky beach of a river or a sea you can find these nice rounded pebbles. They started out as sharp rocks back up in the mountains upstream but when they near the sea they have become beautifully rounded.

The image below shows these pebbles on Earth, and on Mars. The NASA Curiosity rover took the left picture when it investigated a streambed in Gale crater. So here we have pebbles of the same scale, both most likely formed by water, but on different planets.

Okay, so Mars and Earth both have pebbles. That’s nice, but we can kind of already envision this because the images we get back from Mars are so Earth like, with similar beautiful
sunsets. Mars, as shown by the various landers, looks like a dry desert filled with rocks and dunes. There are quite some places on Earth which look the same.

To get into weirder territory, please have a look at the left image. This image is taken from the surface of Titan, a moon of Saturn. Titan and Saturn are even farther away from Earth as Mars. Titan is a cold but active place. I’m not talking about life related activity, I’m talking about it having an active weather system.

On Earth the weather is caused by water. Water evaporates into the air and falls back onto the surface as rain. Titan also has rain, but not consisting of water. Methane acts on Titan like water does on Earth. So you have methane clouds, methane rain, methane seas, methane lakes and methane rivers.

It was in one of these river beds the Huygens probe landed. Luckily it didn’t land in a methane sea! So what did it see? You get it, pebbles. Amazingly these pebbles are made of water ice. It’s so cold on Titan that water is probably always solid and acts like a rock.

So whether you’re on Earth, Mars or Titan the physics of our universe works in a predictable way forming similar patterns. I find that amazing.