Map of the thickness of the ice on ENCELADE. Yellow tints and orange indicate a lesser thickness whereas the blue indicates the maximum of the thickness. © Geophysical research letters.
I am fascinated by the planets and I want to become an astronomer. I intend, over the next two years, to prepare the Physics, Chemistry and Engineering Science entrance exam to an Aerospace school.
Space is always in the
news. New orbits are discovered every year. Thanks to the many satellites around
Earth, we discover ever more things in the infinite space which surrounds us.
A particular topic
fascinates me: is there life on ENCELADE?
ENCELADE (S II Enceladus)
is a natural satellite of the planet Saturn discovered by William Herschel in
1789. It is the sixth satellite of Saturn by its size. It is 500 km in diameter.
It gravitates around Saturn within the most external and the most tenuous ring
of all, called ring E. It possesses a gigantic ocean 45 kilometres deep which
is covered in an ice sheet about twenty kilometres thick. But, at the poles,
the thinner ice (less than 5 km thick) allows powerful jets of vapour and ice to
escape. It is caused by heating due to the intense tides caused by the
closeness of Saturn.
In 2004, NASA sent the CASSINI probe on
Saturn to collect data. According to the CNRS (the French NATIONAL CENTER FOR
SCIENTIFIC RESEARCH): "the data supplied by the Cassini probe was
contradictory until now". After seven years of analysis of the images
captured by the Cassini probe, ENCELADE apparently oscillates on itself… Astronomers
consider that this is due to the presence of an important liquid layer between
the core of ENCELADE and its ice-cold surface.
The results of the study,
published in the magazine "Geophysical Research Letters," describes
the moon’s poles as covered with an ice sheet thinner than had previously been
thought. If this model turns out to be exact, it also proves the presence of an
intense heat production in the deep core of ENCELADE. The researchers now favour
the hypothesis of an intense heat production in the rocky core and a big ocean
which, in this new model, represents 40 % of the total volume of the satellite.
And, because its salt content is considered as equivalent to that of the oceans
of the planet Earth, ENCELADE now seems more than ever, according to the CNRS,
to be a very good candidate for a space mission to look for the presence of extra-terrestrial
life.
Since this news was announced
by NASA during its conference on April 13th 2017, all the media have
been speaking about it (cf. LCI TV for example). The review SCIENCE ET VIE
explains that, during the "New discoveries on the extra-terrestrial
oceanic worlds" conference, NASA announced that ENCELADE was "liveable."
The Cassini probe actually detected hydrogen in the panaches of vapour which
appear from weaknesses of its cracked ice floe. The American review SCIENCE
explains that the vapour and particles contained 1,4 % hydrogen and 0,8 % carbon
dioxide.
These elements are
essential in methanogens, the chemical reaction allowing (on Earth) germs to
live in oceanic depths which sun rays cannot reach. However, if newspapers such
as LE PARISIEN or THE BARBER keep announcing the news, most of the scientific
journals and NASA explain that life is still only a hypothesis. ENCELADE is
covered with an immense ice sheet that is hard as steel; also, an atmosphere is
essential for life…
However, heat, water and organic
matter are indeed present on ENCELADE. For LE PARISIEN and LE FIGARO and most television
channels and radios, this is enough to prove the existence of life. Only the
scientific journals and, of course, the official sites (like NASA and the CNRS)
give us a more complete picture.
If life does exist on this
moon, it will certainly be marine life. Because of the thickness of the ice,
animal and plant species are going to find it difficult to reach the surface to
develop there.
ENCELADE is 1,272 billion kilometres
from Earth. A manned space flight would surely take too long. However, this
discovery remains one of the biggest discoveries of this year. It shows that life
is possible outside Earth.
Sources:
- Science journals: SCIENCE ; SCIENCE ET AVENIR ; SCIENCE ET VIE
- Newspapers: LE PARISIEN ; LE FIGARO
- Officials websites: NASA ; CNRS
- Television: LCI
- Radio: RTL
Ronan SIMONNOT wants to become an astronomer.
