Europa Multiple-Flyby Mission

today I am going to write about proposed mission to investigate Europa.

Europa Multiple-Flyby Mission is a plan consisting of orbiter and a lander directed towards Jupiter‘s moon.

The reason why to choose Europa is quite clear. There is probably liquid water under its surface and if one launches such a thing, it might get public’s attention.[1] (Which might be now more important than ever considering how Trump wants to cut down NASA’s budget especially on the most important thing that they do: Earth’s climate monitoring.)

First of all the orbiter, which would be launched in the next decade, would learn as much as it could about the surface of the moon, Jupiter’s magnetosphere (see later), weird water

Composite image of Europa superimposed on Hubble data

This is two images of course. The original does not have the Europa in middle but only black spot. You can see the plumes on roughly 7 o’clock.

plumes and so on. There are 9 instruments together planned.

Instruments on those orbiters are able to collect data faster than we can receive it. This is because there are more mission that need attention of our receivers. Those are not some small receivers but specialized ones and all missions have some time to send information. For example New Horizons, just from its flyby of Pluto kept sending data for some 6 months.

In case of Jupiter oriented mission this might be a problem because Jupiter has extremely strong magnetosphere which will probably damage the instruments in matter of few weeks. This way it is best to get close to Europa and then get away as soon as possible and send the data later. This can not be done for the lander so it really lasts in matter of days. (Yes, it is still a problem even if you cover your equipment under 150 kilograms of titanium as is planned!)

The lander is thing planned even further into future, around 20 years or so. Much can change and we will see what the priorities are at that point.


[1]People will probably get quite excited by mission promising founding signs of extraterrestrial life.

Moons of our Solar System: Io

it has been couple of posts since I last wrote about moons ofour solar system. Today I will write about the last Galilean moon: Io.

Pravdivé barvy pořízené během cesty sondy Galileo

Io is kind of hellish world. With extreme temperatures and extremely poisonous chemicals, everywhere. Still it has suprisingly beautiful colors and this piece of strange rock is very important component in Jupiter‘s system, lets see why.

Io was with the rest of Galilean moons found out first by Galileo and Simon Marius who gave her the name: Io which was pristess of Hera. She was also Zeus’s lover as it happens frequently.


The picture which is above is taken in true colors and there is yellow red and brown because of certain element. You probably remember this one: sulfur.

There are also various kinds of silicates, this is stuff that contains silicon. Otherwise sulfur dioxide and all other various compounds.

What really suprised scientist when they saw the surface for the first time was that there were and are not many craters. They wanted to date how old the moon is but it surpised them what they found. The surface is in this feature similar to Earth. There are almost no craters because of its geologic activity (othewise rare) which transforms the top layers all the time.

There are more than 400 active volcanoes. Io, is the most geologicly active thing in whole
known Solar System.

There are roughly 150 mountains on the surface ranging to even higher heights than Mount Everest. There are not very steep because there is a huge erosion causing stuff to smooth out. Those mountains were created by the push of the litosphere going down while some parts went up. There are also special features called paterae. They are similar to what on Earth we call caldera which forms as you can see on the right.

This particular picture shows the formation of Crater Lake in state of Oregon, I have been there and I must say that it is something extremely beatiful!

Otherwise the surface is cold, about -143°C but there are some areas around volcanoes which are heated up to even 17°C.


For a long time humans just saw Io as a point in the sky with magnitude of 5. It took the first probes to actually observe something about it except roughly the color.

Pioneer 10 and 11 launched in 1972 and 1973 respectively were the first probes to collect some data.

After that famous Voyager 1 and 2 did another flyby collecting even more data followed up by Galileo and New Horizons.

Orbit, size and atmosphere

The orbit of Io is in resonance with Ganymede and Europa as I already mentioned before. This creates tidal heating through friction causing all this geological activity. Io orbits as fifth moon from Jupiter but it is the closest one of the Galilean moons. This means roughly 421,700 kilometers and one orbit takes 42.5 hours, the moon itself does not rotate because it is tidaly locked to Jupiter.

Io is just a little bigger than Moon, by about 5% which means diameter 3642,6 kilometers but far greater mass (+20%). Io is very dense moon.

There is even atmosphere but it has the pressure of about one billionth of our atmosphere. It is mostly composed of oxide disulfide. If some probe would land there it would not be able to use parachute and it would not need heat shield to prevent from burning. To slow down, it would have to use its rocket nozzles.

What is really interesting is that it interacts with Jupiters magnetosphere which takes out about one ton of material from Io. Io also works as giant generator creating electric field which would kill human in matter of minutes with the power of 400,000 volts and 3,000,000 ampers.


Io picture
Caldera picture

Moons of our Solar System: Europa

here comes the post about another moon of our Solar System. This time it is Europa. Europa the awesome moon with so white surface and those red streaks across but still the smoothest crust, Europa another Galilean moon!

Europa is very famous moon. It is also very large, sixth moon in whole Solar System and 15th object in size in whole System.
Europa-moon.jpgLike all other Galilean moons this one was also discovered by Galileo Galilei who named it Jupiter II and independently by Simon Marius who called it Europa after Zeus’s lover.

I think that Europa is very well known do to popularization of high chance of extraterrestrial life there. Probably also because of that enormous water ocean under its surface.

First of all lets look at its enormous size.

On the right you can see for comparison the size of Europa, Moon and Earth.

Mean radius of Moon is 1,737 km while for Europa it is 1,560 km. Mass of course is lower. This corresponds with density. There is 0.3 g/cm3 difference, which is not much.

Moon orbits at 380,000 km while Europa at 670,000 km. As I said in previous posts Ganymede, Io and Europa are in orbital resonance.

This means that Europa’s interior is heated by friction.

Surface of this moon is the smoothest in whole Solar System. This seems to be from the process of water running from under the crust of ice and smoothing everything out. While there are no high features, you can find there things called penitentes. Those can appear on Earth in high altitudes when snow sublimates in temperatures below zero. It creates those snowy spikes.

If you look on the first picture of whole satellite you can see that there are those red stripes.
It seems that they are created by “hot” ice flowing sometimes from under the surface. This also hints to plate tectonics on other object than Earth.
There is extreme radiation on Europa, about 5,400 mSv which is a lot and it would kill you in about a day.

Under the surface which is made of silicate rock and ice is gigantic ocean of liquid water. It is liquid because of pressure and the friction which causes its temperature to rise.
This is why astronomers think that there could be life.
There are some missions planned, one of them is very interesting and it requires some robot to land on Europa and by heating to melt down through the ice crust towards the ocean. The heat would be made by radioactive fuel.
This thing would have to be very well sterilized so it wont find its own bacteria in the ocean. Hydrobot (on the right) would be dropped there and then it would collect samples and analyze them right in the ocean.

The volume of the ocean is more than twice as much as on Earth and it may be 100 km deep.

Because of enormous tides made by Jupiter, there are water plumes of water vapor which are 200 km high. Those plumes may carry about 7,000 kg/s of material.

Europa has atmosphere but it is not very thick with pressure of 0.1 micro pascal. This atmosphere is made by ionizing radiation hitting the ground and leaving some free atoms which than become the part of atmosphere. Part of the oxygen in atmosphere is made by process called radiolysis.

To date there were already couple of missions which saw Europa from close distance, while yes, we can see Europa even from Earth because when its whole surface turned to us is lighted its apparent magnitude is 5.27 which is pretty good.

First picture taken from close distance was this one on the left. It’s Pioneer 10s picture.
Also Pioneer 11 saw him year later (1974) and after this Voyager 1 and 2 took much better pictures. First satellite to orbit Jupiter was Galileo which was working for 8 years and then it’s course was changed towards Jupiter’s atmosphere.

For now there are planned some missions that would again orbit Jupiter and collect data about its moons especially Europa because of the ocean.
For direct studying of Europa there is planned mission called Europa clipper, which would investigate its habitability and also planned is JUICE – Jupiter Icy Moon Explorer, but this one would be mostly observing Ganymede.


All pictures are from here.

Moons of our Solar System: Jupiter´s moons, Prologue

today I will continue to write about moons. Now I will be stucked on the moons of Jupiter for while since it seems that there are about 8 worth a separate posts so this will take some time and today I will try to introduce them.

So for now there are 67 confirmed moons of Jupiter which is most in the whole Solar System. They are named after Jupiter/Zeus´s lovers daughters etc.
After while we run out of those names so we started to repeat them with little changes like: Ganymede>>Ganymed
Callisto>>Kallisto and so on. All moons of Jupiter are tidaly locked.
Those moons are in different groups and the most important are Galilean moons.

Galilean moons are four moons discovered by Galileo Galilei. He discovered them in the year of 1610 even that there are some informations saying that before him chinese found them. What is sure is that independently day after Galileo, Simon Marius found them too and he was the one who gave them the names we use now (before we called them Jupiter I, Jupiter II…).
From left to right you can see on the picture: Io, Europa, Ganymede, Callisto. All of them except Callisto interact through gravitation, they heat each other´s interior through friction.

On the right you can see Galilean moons from Celestia with their orbits. The pie graph shows mass of moons.
Second group really worth mentioning is Amalthea group (beatiful name). Those are inner satellites which orbit really closely to Jupiter.
Members of this group are: Amalthea, Thebe, Adrasthea, Metis.

Amalthea PIA02532.pngBelow you can see picture of Amalthea.

On last picture are the other moons with their irregullar orbits, there arises a question how much should they be considered moons when they are so small.


Pictures taken from: —> here you can find table of all Jupiter´s moons.

Crash Course video Jupiter´s moons