Europa's surface

Europa is a pretty exciting place.

The smoothest known object in the solar system, it isn't only famous for its good looks. It's the sixth closest moon to the gas giant Jupiter, and has what is assumed to be a nickel core and an atmosphere that, while fragile, holds oxygen. It is famous for being discovered by Galileo in 1610, but  has not - as yet- been explored in any great detail by spacecraft. That, it seems is all about to change as both NASA and the ESA are primed in a race to reach the enigmatic moon.




Europa's tie to the host planet Jupiter is emphasized in her name.

While Jupiter is named after the king of the Roman Gods (aka Zeus in Greek mythology), Europa is named after one of his conquests.
For anyone familiar with Greek mythology, it's well known that Zeus was a randy deity and his wife Hera was less than impressed with his affairs. When Zeus happened upon Europa and her companions he was transfixed with her beauty and transformed himself into a white bull that was so stunning and gentle in appearance that all the women gathered around to fawn over the creature. He laid down in front of Europa and she climbed onto his back. Suddenly the bull jumped up and charged off a cliff, diving into the water below to swim out to sea with her trapped on his back. Zeus took her to Crete and  promised her that she would bear famous sons who could claim that they had a god for a father.

The real life moon mirrors its namesake in many ways. It is one that is very closely tied to water: it is believed that the crust is ice but, due to the position and shifting gravity of being so close to Jupiter, that under the surface there is liquid water. And, just as Europa begot famous sons, so too do many scientists believe that of all the places in our solar system, Europa is the one that is the most likely to birth life. Across its smooth surface, in the ice cracks, there are mysterious blooms of crimson - could these be related to the excretions of huge numbers of micro-organisms in the sea below?





The Race to Europa

Unfortunately we're not quite at the stage where any spacecraft can land on the planet due to technological limitations, and even staying in orbit with the planet for too long is dangerous for the machinery due to Europa's intense radiation fields. But nevertheless NASA and the ESA (European Space Agency) have both put forward missions and been granted funding that will allow them to launch in the mid-2020s. The ESA is currently pulling forward in the lead with the more solid date of 2022 for launch with their spacecraft 'JUICE', to reach Jupiter in 2030.

Artists impression of JUICE: ESA/AOES

JUICE stands for the 'Jupiter Icy Moons Explorer' which, if we're honest, in the world of acronyms is a bit of a cheat. Nevertheless it's plan is impressive: it is planned to set out to Jupiter to study the gas giant and, upon reaching the neighbouring Ganymede enter into humanity's very first orbit with an icy moon(!). The spacecraft will also make flybys of Callisto and Europa using various camera, spectrometers, a radar, altimeter and plasma sensors to monitor the composition of each moon and planet that it comes across, with radiation shielding to protect it and solar panels to power it on its journey.
Jupiter's moons cover a huge range of environments from volcanic to icy to rocky, so it is thought that the data gathered here could give us vital information about how similar planets in our solar system and beyond operate. Most importantly in this mission, it will give vital insights into the composition and behaviour of Jupiter - one of the largest and most alien of planets in our solar system.

Artists Impression of Europa Clipper

NASA's 'Europa Clipper' is perhaps more fully focused on the moon itself than its ESA counterpart. The plan is to place it in orbit of Jupiter and set it on a long looping orbit that would allow it to enact  45 repeated close-quarter flybys of Europa. On board there are plans for a radar to penetrate down into the crust to measure its thickness, an infra-red spectrometer to investigate what the surface is made of and an ion and neutral mass spectrometer to analyse the moon's atmosphere.









Clearly we have a whole lot to look forward to...





Sources

• NASA's 'Europa Clipper' 
• The Gaurdian: NASA Europa Mission has people excited.
• The Mary Sue: NASA planning a mission to Europa to see if its habitable.
• The Official ESA: JUICE site
• 'JUICE is Europe's next large science mission'
• ESA JUICE spacecraft information

Some months ago there was a brilliant BBC-original TV series called Wonders of the Solar System, hosted by Brian Cox. 

Snottite Cluster by Kenneth Ingham

The series explored our whole solar system, exploring alien moons and what conditions allow our own planet to thrive, as well as questioning what was needed to find life in our own solar system.

It's one of my favourite documentaries (heck, almost anything with Brian Cox at the helm is brilliant) so I thoroughly encourage you to grab the DVD where Prof.Cox explores this week's topic with a hell of a lot more class (and budget!). You can pick up Wonders of the Solar System along with it's equally excellent sibling Wonders of the Universe here.


With all that said, if you're still here why not pull up a chair and we'll talk about one of the most intriguing creatures on our planet: Snottites.



What are snottites?

Like Slime Moulds, Snottites are not the most appealing of creatures. In fact, they're rather aptly named, but they are a remarkable scientific discovery. Appearing like a long strings of snot, they are in fact large colonies of single-cell bacteria.

Snotties live deep in caves all over the world, including North Wales, but perhaps one of the most interesting habitats for them is in Cueve de Villa Luz in Tabasco in Mexico. Here, the cave that they call their home is full with utterly toxic hydrogen sulfide gas.

Snottites are not alone in this environment, which has pools of acidic water housing pink fish and crabs closer to the surface. But deeper down, in the dangerously toxic environment the snottites thrive. Away from the sun, the Snottites are nevertheless above to do something remarkable: they can metabolise the deadly hydrogen sulfide, react it with oxygen and produce the equally deadly sulfuric acid. 

Credit: Daniel S Jones, Penn State

So what?


The sulphuric acid that snottites produce is as strong as battery acid and clearly is dangerous for humans, but it shows the very important fact that life can exist in environments that we once thought could only be barren. If snottites can metabolise in this way, then there is no reason why similar creatures can't do the same on hostile worlds.

Snottites' ability to live has become more important than ever, as recent exploration of Mars showed that it was covered in a network of caves which could be potentially open to exploration. It is now widely believed that Mars itself once held running water over its surface due to numerous canyons, horseshoe 'waterfalls', and other geographical structures that indicate the presence of water in it's past some 3 billion years ago. Furthermore traces of gipson also indicate that water was available on the surface. While the water was gone when Mars' temperature dropped and it's atmosphere was blown away by solar winds, there is the possibility of water in either liquid or ice form under its surface...in these caves.
Naturally the environment would be hostile but if snottites can subsist on hydrogen sulfide could life be supported below the surface, in these caves, where the environment is not quite so harsh as the surface?

Caves on Mars (Wikipedia)

Methane blooms on Mars

Another interesting feature of the Mars explorations was the discovery of large methane plumes which seemed to vary in seasons. These plumes still remain a mystery as, in 2001,the Curiosity rover attempted to measure the methane in the atmosphere and came out empty handed, despite the estimates that even only one plume contained 19,000 tonnes of gas. While scientists are baffled, it seems that Mars is cycling it's methane six hundred times faster than Earth, which means that there have to be major sources and pools of the gas that are creating this seasonal behaviour.

While one possible explanation is geological (see the 'mud volcanoes' that erupt methane from beneath the surface of the earth), many people are excited that this may be evidence of life on the red planet. 90% of all methane in our own atmosphere is created by life and a huge part of this is created by archaea bacteria.

What are archaea bacteria, you ask?

Hydrothermal vents in the sea

Why, our old friends the snottites and their cousins.

 Archaea bacteria have been found in some of the most hostile places on Earth. For example on the ocean floor, at 100 times atmospheric pressure and above, around hydrothermal vents that superheat the water to 300 degrees C and spew out sulphur...you can find the archaea coating the ocean floor.

While the need for water appears to be universal for life, just how much water is needed, and how full of other chemicals the environment is, are flexible. At a microbiological level it seems that life can be very hardy and very creative indeed.



But Mars is not the only place that could support alien life in our solar system

Europa

 Perhaps even more exciting than Mars as a place to support life snottite-like or otherwise, is the beautiful white moon of Europa. This moon of Jupiter is covered in a complete crust of ice that is interspaced with mysterious red lines. Looking on the surface, the ice has visibly cracked and shifted unusual distances before reforming, suggesting that underneath the ice there could be liquid that is potentially 100 kilometres deep or more. The strange red lines could potentially be blooms of colour associated with the activity of microbes.
Studies in Iceland have shown that there are some tiny micro-organisms that can actively live in frozen ice and secrete their own antifreeze proteins to create little pools of liquid water for them to live in.

Whether life takes on the shape of slime-moulds, other archaea bacteria, or the tiny ice-dissolving microbes that wriggle around in ice-caves, it seems clear that there is a huge potential for at least simple life to live and possibly even thrive on other planets.

All it takes is a little time and whole lot of research and maybe, just maybe, we're not as alone as we thought in the universe.


Sources
- The BBC's Wonders of the Solar System
-Why Evolution is True: Snottites
-Snottite in Cambrian Mine
-Extremofiles: at the Living Moon
-Caves of Mars project (Wikipedia)
-Mystery deepens as Martian methane eludes Curiosity (New Scientist)
-The Meaning of Mars' Methane: Signs of Subsurface Life? (The Daily Galaxy)