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Cidersomerset
20th March 2013, 22:24
Interresting article..

BBC ONLINE.....

20 March 2013 Last updated at 10:06

Ice blades threaten Europa landing By Paul Rincon
Science editor, BBC News website, The Woodlands, Texas
Jagged blades of ice may cover the equatorial area of Europa

http://news.bbcimg.co.uk/media/images/66445000/jpg/_66445467_66333484.jpg

Jupiter's icy moon Europa is a prime target for future space missions as it harbours a
buried ocean that could have the right conditions for life.But attempts to land may face
a major hazard: jagged "blades" of ice up to 10m long.A major US conference has
heard the moon may have ideal conditions for icy spikes called "penitentes" to form.

Scientists would like to send a lander down to sample surface regions where water wells
up through the icy crust.These areas could allow a robotic probe to sample a proxy for
ocean water that lies several kilometres deep.Details of the penitentes theory were
announced as scientists outlined another proposal to explore the jovian moon with
robotic spacecraft. On Earth, these features (so named because of their resemblance to
the pointed caps worn by "penitents" in Easter processions around the Spanish-speaking
world) form in high altitude regions such as the Andes.Here, the air is both cold and
dry, allowing ice to sublimate (turn from a solid into vapour without passing through a
liquid phase).Penitentes begin to form when irregularities in the surface of the snow are
enhanced by the Sun's energy. These furrows then act as a trap for solar radiation, and,
as they deepen, the tall peaks are left behind.

Sun overhead

Dr Daniel Hobley, from the University of Colorado, who presented his research at the 44
the Lunar and Planetary Science Conference in Texas on Tuesday, said the formation of
penitentes also required the Sun to be overhead as much as possible.



Europa

http://news.bbcimg.co.uk/media/images/56754000/jpg/_56754680_c0088727-structure_of_europa,_artwork-spl.jpg

pAGKpETmJVw

Europa was discovered - together with three other satellites of Jupiter - by Italian astronomer Galileo Galilei in January 1610.
The icy moon is 350 million miles from Earth, and is one of 64 Jovian satellites.
In the 1990s, Nasa's Galileo probe sent pictures back of its surface.
Europa has a small metal core (light blue, centre), surrounded by a large layer of rock (orange).
The surface is thought to consist of an ocean of liquid water (blue) covered by a thick layer of ice (beige).
Jupiter's moon

"Light coming in at a high angle will illuminate the sides of the blades, causing them to
retreat away," he explained.On Earth, this restricts them to between 30 degrees latitude
from the equator."Europa is very strongly tidally locked to Jupiter and Jupiter is very
strongly tidally locked to the plane of the Sun. So the Sun is always coming down
straight from above on Europa," said Dr Hobley, so the moon fulfils this requirement
nicely.He added: "You need a strong thermal gradient between the spike at the top of
the penitente and the pit at the bottom. So any mechanism that acts to suppress that,
i.e. warm cloudy days - or hot air - will also kill them." With its negligible atmosphere,
this wouldn't be a problem on Europa, suggesting the moon could have more or less
ideal conditions for the formation of these icy blades."From our point of view, if the
surface of Europa is subliming - if it is being sculpted by the sunlight - it will form these
features," Dr Hobley told BBC News."The question then becomes: can it sublime the ice
to produce these features faster than other processes that might erode the surface."

Using the angle of the Sun, the team was able to estimate temperatures on Europa's
surface. This in turn allowed them to calculate that penitentes are probably restricted to
between 15 and 20 degrees latitude from the equator. They also estimate that the
penitentes within this region are likely to be between 1m and 10m in depth.
Outside this region of latitude, other erosional processes can outcompete penitente
formation. These include "sputtering" erosion - the bombardment of the surface by very
fast charged particles (a process similar to sandblasting) - and impacts by meteorites.

But Dr Hobley added: "We are expecting a band around the equator where it is… spiky."
There is a limit to the lifetime of these features: Europa's surface is relatively young,
having been resurfaced by currently unknown processes some 50 million years ago.
"If we're on crust that's about 50 million years old and we're near the equator within the
plus minus 20 degree latitude band, we're expecting to get 5m deep, spiky things that
you really wouldn't want to send a lander onto."
Regions of the icy crust may also "wander" from their original location. This could
transport penitentes beyond the ideal latitude band, but may also limit their formation.

Potential problem

Dr Javier Corripio, a glaciologist who has studied the formations in the Andes, said Dr
Hobley had come up with an "interesting hypothesis".However, he highlighted a
potential problem. During the formation of penitentes, the furrows deepen such that
they are sufficiently sheltered from the wind for melting to occur - which helps further
deepen the depressions.

California Institute of Technology

Dr Corripio told BBC News: "I have always seen some melting at the bottom of the
penitentes, and never found them in very cold snowpacks, which is the case on Europa."
He suggested that another process could be active on Europa's surface: "Since
temperature and atmospheric pressure are very low, sublimation rates are also very
low. Then, vapour may simply migrate from areas of high pressure to areas of low
pressure, causing a very slow growth of snow crystals."But he added: "In any case, it is
a situation worth considering for future missions to that moon." Indeed, Dr Hobley may
have a way of testing the idea. Because of the way the Sun moves across the sky,
penitentes should be oriented in an east-west direction. This might be visible as a
polarisation in measurements of the surface. Dr Hobley pointed out that there was a
band around the moon's equator that is "anomalously cold", which means that it holds
on to heat better than other regions of the surface. Penitentes may or may not provide
an explanation, but heat would tend to bounce around the blades rather than being
fired back out.In the near-term, scientists would like to send a lander to the surface
to "taste" the ice in regions where liquid water surges up to Europa's surface from the
vast ocean beneath. A study released this month found further, strong evidence that
salty water makes its way out to Europa's frozen exterior.Co-author Mike Brown from
the California Institute of Technology (Caltech) said: "We now have evidence that
Europa's ocean is not isolated - that the ocean and the surface talk to each other and
exchange chemicals."He added: "If you'd like to know what's in the ocean, you can just
go to the surface and scrape some off."

Nasa had planned an orbiter mission with Europe's space agency, called the Europa-
Jupiter System Mission (EJSM) to have launched in 2020. But the project was
abandoned because of budgetary concerns.At the LPSC, US researchers associated with
the EJSM outlined details for another proposal to explore the jovian moon. Europe also
hopes to salvage something from the EJSM work through a mission called Juice.

http://www.bbc.co.uk/news/science-environment-21341176

Tesla_WTC_Solution
21st March 2013, 21:23
I would LOVE to see enough advances in the private sector, that we might in our lifetimes get to see humans on Europa and other objects in our solar system...

That picture is really cool -- really shows what the problem is! lol