My Favourite Places in the Solar System

Here I’m going to show you some of my favourite places in our solar system. They’re in no particular order, partly because I don’t think I can pick out an absolute favourite. I’ll provide some pictures for each and briefly describe why I think they’re interesting places.

  • Pele Volcano, Io – Jovian Moon

Pele Volcano, Io

Io is a pretty interesting place. Due to various gravitational interactions it is the most volcanically active place in the solar system. Because it’s quite small, volcanic plumes can reach 300 odd kilometers high, as opposed to a few 10′s of thousands of feet on Earth. The most notable aspect about this volcano though is the large red/orangey ring surrounding it (as can be seen in the picture). This is the sulphurous fallout from the volcanic plume. Pretty good start, right?

  • North Polar Region, Saturn

Hexagonal Cloud Pattern

No ice caps up on the poles on Saturn, it’s too big. It’s one of the gas giants. It still has a rather unique and interesting feature though. It’s called the ‘north pole hexagonal cloud pattern’. Not very catchy at all, is it? But it’s a truly bizarre feature. Each straight side of the hexagon is about 14,000km long, making them larger than the diameter of the Earth! No one quite yet knows exactly how it formed or how it works, however, although there are plausible theories.

  • 433 Eros, Near-Earth Asteroid

The Asteroid Eros

Eros is only here because I remember the photos coming through, when I was 10, when the NEAR spacecraft landed on its surface. Some of the larger rocks found on the asteroid are all thought to originate from a single crater from a meteor impact about 1 billion years ago. The asteroids got a pretty funky shape too.

  • Olympus Mons, Mars

Olympus Mons

Olympus Mons just had to make it in here. It’s the tallest mountain in the solar system (technically an extinct volcano) that stands a whopping 22km high, that’s 3 times the height of Everest! How does a volcano grow to be so big? It’s mainly thanks to Mars’ lower gravity. Lava doesn’t rush down at such a speed so has longer to cool in a given place. Also, it’s thanks to a mantle plume that used to sit beneath the volcano. This is where magma rises from the deep to the surface. We have these mantle plumes on Earth, but because of plate tectonics they move around and don’t stay in one fixed location, which is partly why we don’t have anything as impressive!

  • Verona Rupes, Miranda – Uranian Moon

Miranda

Now for one not so well known. We venture much farther out to a moon orbiting Uranus, Miranda. We’ve only had a brief glimpse of Miranda, thanks to the Voyager 2 spacecraft, so not all of it has been imaged. It’ll probably be another 50 or more years before that’s done. But from what we’ve seen it looks like a pretty cool place, it’s got some interesting geological features, in fact it’s the most geologically diverse moon of Uranus. Verona Rupes is the tallest cliff in the solar system, up to 10 km high. Imagine looking all the way up at that! It’s not known how it formed, although it’ll either be from an impact or crustal lifting.

  • Kraken Mare, Titan – Saturnian Moon

Radar Image of Kraken Mare, Titan

Titan ranks as possibly the most interesting place in the solar system. It’s the second biggest moon around (larger than the planet Mercury) and it’s enveloped in a thick atmosphere, thicker than the Earth’s. Titan’s sometimes referred to as a primordial Earth in deep freeze. That’s because it’s thought to resemble how the Earth looked a couple billion years ago, but in deep freeze. The most unique feature though is in relation to its temperature. At  about -175°C methane can remain in 3 different states – a gas, a solid and a liquid, much like water can on Earth. As a result there are large icy patches of frozen methane, a nitrogen atmosphere with many different hydrocarbons and there are large lakes of liquid methane, of which Kraken Mare is the biggest. It’s also the only other place in the solar system where it rains. Not water but methane, which drifts slowly down because of its lower gravity. What an amazing sight that would be!

  • The Rings of Saturn, Saturn

The effects of a moonlet on one of Saturn’s rings

What would this be if we didn’t discuss the majestic rings of Saturn? Made from trillions upon trillions of ice particles, some microscopic some up to a few metres in length, they are so bright because they’re mainly made from water ice and reflect a lot of the Sun’s light. They’re incredibly thin too, no more than a few metres thick! Amazing for such a vast system of rings. It’s thought over time these particles coalesce and then break apart, and the cycle continues. Some of Saturn’s little moonlets cause bizarre gravitational patterns in the rings too, and this is also partly why there are gaps between some of the rings. The moon Enceladus also provides material for one of the rings. More on that shortly though. The biggest question though? No one really knows how the rings go there in the first place.

  • Tycho Crater, The Moon

Central Peak of Tycho Crater

The only reason this one made it in is because of a photo taken by the Lunar Reconnaissance Orbiter a few months ago. It’s quite a young crater (just over 100 million years old), easily seen with the naked eye and a favourite observing point for amateur astronomers. The crater has a central peak. This is where, moments after the impact that created it, material from deep below rebounded forming a small mountainous area in its centre. This is typical of most large impact craters. LRO took a photo of this central peak, and you can see so much detail that you can even make out a large boulder right at the top it. Impressive stuff, huh? (Click on the image to see the bigger, better version)

  • Tiger Stripes, Enceladus – Saturnian Moon

False colour image of the jets from the Tiger Stripes

Enceladus is a pretty special place. It’s a tiny little moon, so tiny in fact that it would nicely fit in the North Sea between the UK and Scandinavia. Like the gravitational interactions that make Io active though, Enceladus is active. Not with volcanism but with cryovolcanism (basically icy volcanoes – counter-intuitive, I know, but it really does happen). The Tiger Stripes are where it’s most active. Heat from inside melts icy products and a phenomena similar to geysers on Earth are produced, launching the icy products out into space. This creates Saturn’s outermost ring, the E ring. Due to the gravitational interactions warming the moons interior up it’s also possible that a liquid water ocean exists beneath the surface!

  • Conamara Chaos, Europa – Jovian Moon

Conamara Chaos, Europa

Another world shaped by cryovolcanism now, Europa, the moon lying slightly further out than Io. Whilst not as active as Io, and a tad cooler too, Europa remains the most exciting place in the solar system for the possibility of life. It has a thick icy surface, below which probably lies a massive liquid water ocean. If this exists, which is quite likely the case, then life, extraterrestrial life, could be there too. Chaos terrain is called as such because it’s pretty chaotic, there’s a lot that has been going on, as can be seen by the image. The area consists of icy rafts that have moved around and rotated, it’s all surrounded by a ‘matrix’ of jumbled up ice blocks too. Pretty hectic indeed!

  • Cantaloupe Terrain, Triton – Neptunian Moon

Triton’s south polar cap and cantaloupe terrain

Well I’ve got include a place that has such a cool name, haven’t I. This terrain on Triton is named Cantaloupe terrain because it looks like the skin on a cantaloupe melon! Triton is Neptune’s largest moon and it has a mysterious past. The moon goes the wrong way around the planet. Could it be a captured Kuiper belt object, now locked into orbit? Or did Neptune devour another planet billions of years ago and steal one of its moons? What is interesting about this place though is that its geologically active, again with cryovolcanism. It has geysers expelling nitrogen. These geysers appear to be powered by solar heating, which is odd because it’s so far away from the Sun, it seems to have a profound effect though! The Cantaloupe terrain itself is thought to have formed by a process called diapirism, similar to how a lava lamp works.

  • Taurus-Littrow Valley, The Moon

Orange soil on the Moon!

Back to the Moon now and the landing site of Apollo 17, the last manned mission to the Moon. This makes it in here because of something very interesting Jack Schmitt found (the only scientist to have been to the Moon). We all think of the Moon as a fairly mundane place. It’s just grey and boring…or so it seems. During Apollo 17, the astronauts came across not grey, but orange soil! This orange soil is made up from volcanic glass beads that erupted and solidified in fire fountains during the areas early formation about 4 billion years ago.

  • Valles Marineris, Mars

Topographic image of Valles Marineris

Another of Mars’ unique landscapes. This is one of the greatest valleys in the solar system. You could fit the Grand Canyon into one of the Valles Marineris’ tributaries! It’s 4,000km long, 200km wide and reaching down to 7km deep! It’s thought that this great valley was created by what’s known as rift faulting – that’s responsible for the rift valley too. Erosion by water in Mars’ earlier days may also have helped too.

  • Cassini Regio, Iapetus – Saturnian Moon

The two halves of Iapetus

And last but not least is Iapetus. This is a moon of two deeply contrasting halves. One side is dark and the other a bright white. There’s also has a strange ridge that runs half way around its equator. The dark part of the moon, known as Cassini Regio, is a thin covering of material, only about 10cm thick, that it thought to come not from Iapetus elsewhere. It’s thought that there is also some residue making it up too that has been left behind by the evaporation of surface ice. The ridge is a great complication as it’s not known how it formed, or why it formed nearly exactly around the equator. What we do know though is that it contains some of the tallest mountains in the solar system!

I’d really like to know some of your favourite places, especially if I haven’t mentioned them. Leave them as a comment below along with a brief reason as to why it’s your favourite. 

What do we mean by Earth 2.0?

Over the past few years we’ve started to make some truly remarkable discoveries. Thanks to the Kepler Space Telescope we’re starting to discover the first Earth-sized planets orbiting other stars in the galaxy. We must tread forward carefully though, calling some of these planets Earth’s twin is dangerous, and we’re at risk of not realising the importance when we find the real thing.

The problems started last year with the announcement of the first Earth-like planet, Gliese 581g. The unfortunate thing is is that this planet probably doesn’t exist. More recently Kepler has discovered Kepler-22b, a super-Earth orbiting a slightly smaller star than our own in the habitable zone, the area where liquid water can exist. We don’t yet know though, given this planets larger size, whether it’s rocky or gaseous like Neptune. Yet the media hype this up and only make a small reference to the uncertainties. Just the other day NASA announced the discovery of the Kepler-20 system. Two of these planets are the same size as the Earth, does this qualify them to be our twin?

Kepler-22b – Rocky or Gaseous? We don’t know yet!

Venus is about the same size as the Earth but yet most scientists would avoid calling it our twin. Firstly there’s no water, then there’s the crushing atmosphere, runaway greenhouse effect creating temperatures of 460°C, it rains sulphuric acid. Twin? I think not.

When we do find a real Earth-twin though what do we really mean? A planet the same size as ours in the habitable zone? No, I think we need to go further, much further. An Earth-twin should also have a similar mass to ours. Too much mass and plate tectonics may not operate on the hypothetical world, meaning the surface doesn’t get recycled and there probably won’t be any life. We need to analyse the atmosphere. The James Webb Space Telescope will be able to provide this when she launches, hopefully in 2018. The gases in the atmosphere should be in a similar abundance to ours. We don’t want another Venus! Does it have a Moon? The Moon stabilises the Earth’s axis so it doesn’t wildly fluctuate that would cause catastrophic climatic changes (new evidence suggests a moon may not be necessary however). Only when these criterion have been met can we even start to think of announcing the discovery of Earths-twin.

Space agencies really should define what we really mean by an ‘Earth-twin’. We must be careful with upcoming reports of new planets, there are going to be hundreds more from Kepler over the next few years. We don’t want to become normalised to these discoveries because we’ll miss the significance when we do find a truly habitable Earth 2.0. That day will be one of the greatest days for science in history, let’s make sure we realise it.

Destination: Gale Crater

The decision has finally been made. A giant rover known as Curiosity (or the Mars Science Laboratory) that is the size of a Mini will be launched to make a landing in Gale crater on Mars.

Comparison between Sojourner, MER and MSL

As we’ve said, MSL is huge. The size of mini. Over twice the size when compared to the Mars Exploration Rovers Spirit and Opportunity. The Sojourner rover insignificant in comparison.

Gale crater is pretty big too, 154km across, and is an ideal place for a rover. It’s thought to hold a lot of evidence for past water on the Red planet. MSL itself has been designed to look for evidence of past life, whether Mars was ever habitable at all in its past. The rover will spend 1 Martian year exploring the surface (about 2 Earth years) and if the MER’s are anything to go by, Curiosity should last longer (although they are using different power generating sources).

The rover is also going to carry out the first precision landing on Mars. It’ll be using a very unique and ambitious system, a sky crane. I’d compare it to being as difficult as a manned lunar module landing, as in Apollo. It’s a pretty incredible system.

Curiosity will be launching sometime between the 25th November and the 18th December 2011 and landing between the 6th and 20th August 2012, so keep checking NASA’s website for updates.

Here are two videos showing the operation of the sky crane and another describing what Curiosity will be doing at Gale.

Links: NASA report on landing site selection
Space.com report

 

A New World – Dawn approaching Vesta

Dawn – The journey to the beginning of the Solar System! It’s a fairly ambitious mission, as are most of NASA’s missions at the moment. Firstly the spacecraft uses ion propulsion, a technology tested on Deep Space 1 but never before used for a dedicated science mission. Secondly Dawn has not one but two targets. The large asteroid or even protoplanet, Vesta and then the dwarf planet Ceres. The spacecraft will go into orbit around Vesta, happily do some science for a while, break orbit and then go to orbit Ceres!

Launch of Dawn on a Delta II Rocket

Dawn launched back in September 2007 atop a Delta II rocket. It’s been in the cruise ever since, giving short bursts of ion propulsion to refine it’s orbit. Now after nearly 4 years she’s almost arrived, ready to hop into orbit.

Vesta is the largest asteroid in the Solar System (Ceres is larger but is termed a dwarf planet) it’s about 530km across and is estimated to contain 9% of the mass of the asteroid belt, so it’s a pretty hefty object. It’s thought to be differentiated, that is it’s so big so that heavier elements, like iron, fall towards the centre and lighter elements are found nearer the surface. This is the same way that Earth’s core formed.

We already know a fair bit about Vesta surprisingly. About 1 billion years ago Vesta was hit by an asteroid that’s left a small crater. This threw out lots and lots of debris, and quite a bit of this has fallen to the Earth. These meteorites have the fancy name of Howardite-Eucrite-Diogenite (HED) meteorites. Evidence from these meteorites show that Vesta is between 4.43 and 4.55 billion years old and reveals that Vesta has a history of extensive igneous processes. Infact the meteorites are very similar to magmatic rocks found on the Earth.

The mission at Vesta is to develop our understanding of how the Solar System formed and in particular what role water played in planetary evolution. Vesta and Ceres both reflect what the early Solar System was like, something we can’t figure out here on Earth because of all the geological activity the Earth is still going through. Continue reading