Bonjour,

Non, mais on est sur que c'est de la matière blanche.

Au revoir.
Bernard Lempel
http://lempel.net

"Alain Haïoun" <alain.haioun***orange.fr> a écrit dans le message de news:
48e24533$0$886$ba4acef3***news.orange.fr...

....Couic...

> DEO GRACIAS - La sonde Phoenix a pour le première fois observé la chute de
> flocons de neige à la surface de la planète rouge.
>
> Cette fois on est sûr que c'est bien de l'eau?
>
> Alain

> Bonjour,

Lempel ajouta l'idée :

> Non, mais on est sur que c'est de la matière blanche...

[1.en] http://en.wikipedia.org/wiki/Image:D..._Subliming.jpg

[MODE:COPY ON] Source Wikipedia, the great free online encyclopedia...

On earth (1G]: At −78.51° C (or -109.3° F), *carbon dioxide changes
directly from a solid phase* to *a gaseous phase through sublimation*,
or from gaseous to solid through deposition. Solid carbon dioxide is
normally called "dry ice", a generic trademark.

It was first observed, *in 1825 from the French chemist*, Charles
Thilorier, but on earth of course...

Dry ice is commonly used as a cooling agent, and it is relatively
inexpensive. A convenient property for this purpose is that solid
carbon dioxide sublimes directly into the gas phase leaving no liquid.
It can often be found in grocery stores and laboratories, and it is
also used in the shipping industry.

The largest non-cooling use for dry ice is blast cleaning.

Liquid carbon dioxide forms only at pressures above 5.1 atm ; *the
triple point of carbon dioxide* is about 518 kPa at −56.6 °C (See phase
diagram, above). The critical point is 7.38 MPa at 31.1 °C.

[2.en] see and look that from http://preview.tinyurl.com/46v7bu ?

An alternative form of solid carbon dioxide, an amorphous glass-like
form, is possible, although not at atmospheric pressure.[6] This form
of glass, called carbonia, was produced by supercooling heated CO2 at
extreme pressure (40–48 GPa or about 400,000 atmospheres) in a diamond
anvil.

This discovery confirmed the theory that carbon dioxide could exist in
a glass state similar to other members of its elemental family, like
silicon (silica glass) and germanium. Unlike silica and germania
glasses, however, carbonia glass is not stable at normal pressures and
reverts back to gas when pressure is released

[3.fr] http://fr.wikipedia.org/wiki/Neige_carbonique

À la pression atmosphérique terrestre de [G=1, on earth ground], le
dioxyde de carbone serait jamais sous sa forme liquide... Il passerait
directement de la forme solide Ã*** sa forme gazeuse (et (ou) que par
sublimation, an very stange astrophysic effect, also).

[MODE:COPY OFF] Source Wikipedia, the great free online encyclopedia...

> Au revoir.

(fu2:fr.sci.zetetique only)

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