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Saturday, 17 January 2015

Venus: A hell world, wearing silk pyjamas...

Venus: The smooth blue of the dayside (seen in UV light) contrasts with the infra red view of the night side, showing infernal heat seeping out of the clouds
Despite having cooked up in Venus' atmopshere in December 2014, the Venus express spacecraft keeps giving us new discoveries (link here). JAXA has bought their Akatsuki spacecraft into orbit around Venus, and are preparing for their own science campaign. Terrifying as it is to us humans, Venus is also a fascinating place, so it seems appropriate to look back the discoveries Venus Express made, the incredibly strange world it revealed, and what the future of Venus exploration holds.

Mysteries beneath the clouds:
Once Venus was just a bright, beautiful, point of light to us. Then the space age revealed it as a world like some cosmic lab experiment run wild. The surface is drowned beneath an ocean of supercritical carbon dioxide - the pressure and temperature (450 degrees Celsius, 90 atmospheres) beneath the clouds that the CO2 enters a weird state called a 'supercritical fluid', that is neither liquid nor gas.
On the scalding surface radar images show that there are more volcanoes than on any other planet, and signs of ancient lava flows  - but spotting an active volcano  from a dormant one at the bottom of a ocean of hot, high pressure, CO2 isn't easy. What is clear is that, at some ancient point ,some unknown catastrophe covered the whole surface of Venus in lava, obliterating almost all traces of the world that was there before. 

Above: Take the lava in this video and multiply it by 'the end of the world squared' and you'll have some idea of what it was like on Venus at that time. Courtesy of volcanopixs

It gets odder: Radar scans show a bright coating on the mountain tops, but strange, dark patches covering the highest peaks - the best explanation anyone has is that the mountains get snow.. made of heavy metals:

Above: Yes, this is a very silly pun*. But doing a 20,000 mph death dive into a hell planet ... that is very, very, metal. So this for metalheads everywhere - and next time you're in the mosh pit, think of Venus Express, going down in flames..

But the 'snows' have holes in them that are incredibly dark to radar, much darker than anything else on the surface. That makes no sense, and no-one as a solid explanation (this is not something scientists like to admit, but they really don't).
Above: The radar-bright 'snow', sitting on a plateau on the surface of Venus. Image courtesy of NASA.
If anything makes Venus special, it's that pressure cooker atmosphere/ocean. Topped off with chemically complex sulphuric acid clouds, it's unlike anything else in the solar system. It's also a law unto itself: The atmosphere spins faster than the planet it hides, is full of the odd: Unexplained UV absorbing chemicals in the clouds, bacteria sized particles in its clouds, and an unexplained glow called 'ashen light', to name just a few.
Not only that but, even though the clouds rain battery acid that boils before it hits the distant ground, at 70 km altitude there is a layer that is more Earth like than anything else in the solar system. In fact, after finding organisms that thrive in highly acid conditions, there are scientists who put forward the idea that some of the unexplained chemical imbalances, and hard to produce chemicals, in the Venusian clouds were there due to an exotic form of life...
That was Venus before Venus Express arrived: A high temperature, high pressure physical and chemical enigma. Afterwards.... its still a  high temperature, high pressure physical and chemical enigma. But now we know of even odder things....

What Venus Express saw:

The Venusian day has got six minutes longer since the last probe visited:
On Earth a really massive earthquake can change the length of the day by fractions of a second. Since the last probe visited the day on Venus has got longer by over six minutes. So something big is happening there - we just don't know what.....

The incredibly powerful winds are getting stronger, somehow:
The winds of Venus blow at up to 300km an hour. Since the last probe visited they have gotten faster by 100km per hour. There's no clear reason for this, but, again, something big is happening at Venus.
There's something about the poles of worlds that lend themselves to strangeness. Saturn has its giant hexagon storm, the Moon has the mountains of eternal light and valleys of eternal darkness. Venus has... this...

Above: The twisting vortex(es) at the pole of Venus, shot in infra red , so the heat from the scalding surface can highlight the structure. Courtesy of ESA

When asked 'What the hell is that?' most scientists involved with Venus Express describe it as 'a giant hurricane, with two eyes, sitting right over the planets pole'. Although, over time the central vortexes began to twist into all kinds of shapes, beside the double eye one, so I think  'we're not sure guv' would've been closer to the truth...
At around the time Venus express arrived, some thing injected a massive amount of sulphur dioxide into the Venusian atmosphere. Over time the levels steadily decayed, in a pattern that exactly matches the way a volcanic eruption on Earth throes sulphur dioxide gas into the atmosphere. On top of that there are volcanoes like Idunn Mons which show signs of having fresh lava flows around them:

Above: An infra red map of the volcanic mountain Idunn Mons on Venus. Just being on the surface of Venus is a bad place to stand, so this volcano is the definition of an extremely bad place to stand . Courtesy of ESA

The probe also saw searingly hot flashes from volcanic vents even hotter than the rest of the scorching surface, adding the words 'explosive' and 'lava' to a description of the surface that already reads like hells more unstable cousin.

Venus has an ozone layer, albeit a very thin one. A lot of astrobiologists had a thought that the presence of CO2, oxygen, and ozone in an atmosphere together could only be a result of life... the take home message here is that it's a good idea to check your theories against the facts.

Venus had water, oceans, continents:
Above: Venus, with water -  looks inviting? Fancy a swim? Too bad, it all boiled billions of years ago..

One of missions finds highlights how lucky Earth is to have a natural magnetic force-field keeping the solar wind (a wind of electrically charged particles from the sun) out: It's already known that this wind helped devastate Mars by gradually blasting most of its air into space. Now we know that it does something similar to Venus, but at Venus the victim is the planets water, which is broken down by sunlight, and then whisked off into space by the solar wind... if you work the numbers of how much and how fast backwards, it turns out Venus must have had a lot of water at some point. Like Mars, Venus was definitely a water world.
A closer analysis of the surface also shows that the high plateaus on Venus look differently eroded than the basins, something that would make sense if the basins were filled with water, and the plateaus were continents, in the distant past...

The air really does glow:
The atmosphere contains a chemical called nitric oxide - it gets used a lot in chemical industry here - that makes the atmosphere glow. But this doesn't explain the 'ashen light' mentioned above, as the glow is infra red. Incidentally nitric oxide is such a useful molecule it was named 'molecule of the year in 1992.'

....It's also electrically charged:
All those charged particles slamming into the Venusian atmosphere generate electric currents in the upper layers.

The  acid clouds produce lighting!
Above: Artists impression of Lightning on Venus. Cool. Unless you're riding that balloon.

This was a big question mark before Venus express. Lightning had never been observed in clouds made of sulphuric acid before, and lightning can have surprising effects on the atmospheres chemistry by producing compounds that otherwise would not exist.

Venus is till scalding, still weird, and still fascinating - so what next?

The Japanese Akatsuki spacecraft recently arrived there - it was supposed to enter orbit around Venus in 2010, but a malfunction left it orbiting the Sun. Luckily orbital mechanics offered a chance for it to complete its mission, and use its remaining fuel to enter orbit.

Beyond that.... the are big plans, although nothing concrete: Manned flyby's, balloon probes, surface rovers, even floating cities....

Time will tell.

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