back to article Huge ice blades on Jupiter’s Europa will make it a right pain in the ASCII to land on

Exploring Jupiter’s moon Europa will be a treacherous task, it seems: scientists reckon its surface is covered in sharp towering icy daggers. The menacing shards are known as penitentes, according to a paper published in Nature Geoscience this week. They normally form in dry cold climates, where sunlight melts snow and it …

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Penitentes

So called because of how you'd feel if you fell/landed on them.

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Anonymous Coward

Re: Penitentes

Pointed structures standing upright suggests an etymological root shared with penis. Is that Latin for "sword"?

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Re: Penitentes

No, it's the Spanish word for, well, "penitents", people doing penance. See also the robes and hoods worn by penitents during Spanish Holy Week.

https://en.wikipedia.org/wiki/Capirote

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Re: Penitentes

So nothing to do with eating pasta on a camping holiday, then?

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Re: Penitentes

It's from the Latin for sorry, because if you land on it you will be.

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Anonymous Coward

Re: Penitentes

" Is that Latin for "sword"?"

Apparently old Latin for "tail".

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Coat

Re: Penitentes

Icy what you did there.

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Anonymous Coward

So they haven't discovered anything. they've assumed.

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Assumptions

True, they haven't directly observed them, but this theory explains the observed data and is consistemt with some other information as well, so I'll take this at face value until something better comes along.

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They've assumed

It's more of a proposed explanation than an assumption, but I think there are better explanations.

Penitentes are formed by ablative erosion so the peak of the penitente is indicative of an older and higher surface level - the penitentes are not built up from the original surface but are what's left.after the surrounding material has been removed (by the aforesaid erosion). If we have 15m high penitentes then we need to know where that 15m of eroded material came from and where it subsequently went.

More likely, imo, is that the 'roughness' is due to either compression fractures, similar to what we see in the Arctic ice sheets, or the presence of cryovolcanic 'spines', similar in mechanism to those we see being erupted from lava domes. Neither of these explanations require the now missing eroded material.

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Re: They've assumed

That might be true with earth penitentes but on Europa the ground surface is all ice (with pink bits) so a source of ablative ice is not a problem. I also strongly suspect the physics is a mite different when the sublimating ice is in a vacuum.

But then I'm only a Stamp Collector so what do I know but I do suspect your assumptions are wanting.

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Joke

No wonder...

The aliens told us to "Attempt no landing there"....

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DJV
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Attempt no landing there...

...unless you fancy [a close shave / a Brazilian / castration without anesthetic] or all three on the way in!

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Obvious A C Clarke reference

Now we know why we're not allowed to land on Europa.

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According to Mirriam Webster

Penitente noun

Pen·i·ten·te | \ˌpenəˈtentā, -tē\

plural Penitentes\-ās, -ēz \

Definition of Penitente

: a member of a religious society of Flagellants in Spanish-American communities of the southwestern U.S. (as New Mexico) who practice self-whipping and other forms of penitential torture particularly during Holy Week

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Re: According to Mirriam Webster

Is that Merriam Websters younger sister?

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In the UK we would just say

Its the wrong sort of snow...

Although it does make me wonder if any lander would have to be called a "blade runner"

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Has anybody mentioned Arthur C. Clarke yet?

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Yes.

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Are you sure?

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Yes

It's in my headline from two and three quarter hours before your post, though I was beaten to the reference by seconds.

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Not Clarke, more like a Hugh Walters book, "Journey to Jupiter".

https://en.wikipedia.org/wiki/Journey_to_Jupiter

Okay, so that one has the spiky bits set on a different moon and made of rock but he did have the "here be dragons" sentiment fairly well.

There's an entire series of these. Fun reads if you're not too fussy about what we now consider to be scientific accuracy.

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Does nobody ever read Larry Niven?

Just head there with your personal fusion drive and tickle the surface for a few seconds.

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Mushroom

Re: Does nobody ever read Larry Niven?

> Just head there with your personal fusion drive and tickle the surface for a few seconds.

Requires managing fuel carefully. Just have the host spacecraft drop a small nuke from orbit. It's the only way to be sure...

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Re: Does nobody ever read Larry Niven?

I thought the idea was to look for life on the moon, not to turn it into a ready-meal.

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Re: Does nobody ever read Larry Niven?

Besides, the locals would consider this a hostile act, and respond with a psychic attack (see Niven's "Handicapped").

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Re: Does nobody ever read Larry Niven?

David Niven, perhaps.

Well, his early memoirs.

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Re: Does nobody ever read Larry Niven?

Ah, the moon's a balloon. A most entertaining read.

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Re: Does nobody ever read Larry Niven?

Don't nukes fail to work very well in a vacuum? Also Europa is already bathed in very hard radiation whipped up to relativistic speeds by the local gas giant. Hardening the electronics of any lander so it survives long enough to take samples from the pink crevasses let alone drill through kilometres of likely very hard ice (cf the measurements of comet ice hardness) is very live issue.

The radiation pretty much precludes a manned presence on the surface any time soon barring some very sci-fi levels of technology advancement. But even so, think humans staying in shielded craft and sending the robots out into the radiation storm.

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NASA is planning to send Europa Clipper spacecraft

They're sending a clipper?

Maybe they should be sending an ice-breaker.

... and shouldn't ESA get first dibs on a moon called Europa?

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Anonymous Coward

Re: NASA is planning to send Europa Clipper spacecraft

Maybe they should be sending an ice-breaker.

Let the European Space Agency send a lander first. Then NASA can come along afterwards and land in the relatively smooth crater.

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Coat

Re: NASA is planning to send Europa Clipper spacecraft

Then NASA can come along afterwards and land in the relatively smooth crater

With their 36 inch lander, in the 36 cm crater?

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Anonymous Coward

Re: NASA is planning to send Europa Clipper spacecraft

> They're sending a clipper?

Is it windy? Probably need a zippo

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Re. Icebreaker

Actually they may well send a nuclear powered submarine probe there once all the bugs are worked out/etc.

In order to melt the ice it would need to get up to some 200C for several hours and the best way to do this would be something like a small plutonium source (238Pu) and a heat exchanger.

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Coat

Re: Re. Icebreaker

This method of propulsion would be called the "Astroglide" drive

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aks

Re: Re. Icebreaker

More than a few hours, if the ice crust is as thick as projected. The same concept was suggested as a way to go deep into the Earth. Pressure is another major issue.

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Nanny Ogg's space travels

Her favourite song captures the essence of this planet's defence against alien (e.g. human) interference.

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Re: Nanny Ogg's space travels

Are you sure that you don't mean the product of various researches by Darwin and Huxley and Hall that conclusively proved that the hedgehog has an ingenious first line of defence?

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Re: Nanny Ogg's space travels

Her favourite song captures the essence of this planet's defence against alien (e.g. human) interference.

A Wizard's staff has a knob on the end?

Shirley not?

:)

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Happy

RE: Icebreaker

Spacey McSpaceface?

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Happy

Re: RE: Icebreaker

"Spacey McSpaceface?"

Spikey McSpikearse.

Oh sorry, that's the hedgehog again.

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Facepalm

ASCII

Or as we used to refer to it several years ago 'Arthur's Code'.

This came about because early versions of The Sphere by Michael Crichton spelt it that way.

One of several mistakes in the text, actually. Another was a transmission of a block of digits they receive (and it was only digits in the text) that one character identifies as a hex dump. Shortly after another character claims it can't coming from a 68000 processor "because the 68000 doesn't work in hex".

The film was better. Just.

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This post has been deleted by its author

Duke Nukem

Not if you send in a small tactical nuke to the landing zone first.

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It's not ROCKET science

So we need to invent something that sprays copious volumes of very hot gases out of its underside as it comes in to land, thereby melting any ice spears and creating a smooth surface for eventual touchdown? It'll transform space-flight when that's invented.

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Re: It's not ROCKET science

I'll nominate our entire government strapped to the underside of some suitable vessel. The advantage of politicians is that you do not need to worry about their orientation as they spray copious volumes of very hot gasses out of both orifices.

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Flame

Re: It's not ROCKET science

Sounds like me the day after a really good vindaloo

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Shirley this is wrong

"They found that the regions near the equator reflect radar waves more readily than its poles, and the reflection patterns are best explained by the existence of these icy blades."

If the surface was smooth you would get more reflection at the equator than the poles.

If the surface is covered in penitentes to almost 15 metres or 50 feet in height, with a spacing of 7.5 metres there would be more reflections near the poles than the equator. All those surfaces perpendicular to the radar beam and all.

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You're making a lot of assumptions there

As I read it the penitentes are near the equator (warmer environment aiding sublimation, presumably). So, at the poles the radar signal just disappears into space unless it's pointing straight down. At the equator there are vertical and horizontal surfaces forming cavities which reflect the signal randomly creating a more or less omnidirectional return signal.

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Bah!

Nonsense!

These "ice blades" will flash into steam when bathed in the superheated gasses of the lander's mighty descent stage engine.

The astronauts may then safely walk about on the re-frozen ice-plain with the aid of non-slip space-crampons.

What?

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