A remarkable feature of Europa, one of Jupiter's moons, are the red streaks
that run across her surface. Its chemical composition is puzzling since it
does not like any known material on Earth, despite scientists' suspicions
that it is a frozen combination of water and salts.
With the discovery of a brand-new variety of solid crystal that develops
when water and table salt meet under cold, high-pressure circumstances, a
research team led by the University of Washington may have found the answer
to the mystery. The novel chemical developed in a laboratory on Earth may
form at the surface and bottom of the deep seas of these planets, according
to researchers.
The study, which was released on February 20 in the Proceedings of the
National Academy of Sciences, discloses a novel combination for water and
sodium chloride, or table salt, two of the most prevalent elements on
Earth.
Modern science seldom makes fundamental breakthroughs, according to the
study's principal author Baptiste Journaux, an acting assistant professor of
Earth and space sciences at the University of Washington. "Under Earth
circumstances, salt and water are fairly well known. But beyond that, there
is no light at all. And now we have these planetary objects, which likely
contain substances that are quite familiar to us but are under really
unusual circumstances. All of the fundamental mineralogical research from
the 1800s must be redone, but at high pressure and low temperature. It's a
fun moment right now.
A hydrate is a stiff, salt-coated, frozen lattice that forms at low
temperatures and is kept together by hydrogen bonding. The sole sodium
chloride hydrate that was previously known had a straightforward composition
with one salt molecule for every two water molecules.
But, the two brand-new hydrates, discovered at low temperatures and
moderate pressures, are remarkably unlike. For every 17 water molecules in
one, there are two sodium chlorides, but for every 13 water molecules in the
other, there is one sodium chloride. This would account for the more
"watery" than anticipated signs from the surface of Jupiter's moons.
According to Journaux, "it possesses the structure that planetary
scientists have been hoping for."
New varieties of salty ice have implications for planetary science,
physical chemistry, and even energy research, which employs hydrates as a
form of energy storage, according to Journaux.
A little amount of salty water, roughly the size of a sand grain, was
compressed between two diamonds during the experiment to a pressure of
25,000 times that of atmospheric pressure. The crew was able to observe the
procedure under a microscope because to the transparent diamonds.
As salt functions as an antifreeze, Baptiste said, "we were attempting to
test how adding salt would impact the quantity of ice we could obtain."
"Surprisingly, as we increased the pressure, we saw that these crystals
began to develop that we had not anticipated. It was a really fortunate
finding.
In Jupiter's moons, where scientists believe 5 to 10 kilometers of ice
would cover seas up to several hundred kilometers thick, with even denser
forms of ice likely at the bottom, such frigid, high-pressure conditions
would be typical.
The primary driver of the variation in the crystal structures we
discovered, according to Journaux, is pressure. "Pressure basically pushes
the molecules closer together, so their interaction changes," he
added.
One of the two structures persisted when the pressure was removed once the
newly found hydrates had formed.
We found that it is stable at normal pressure up to a temperature of around
minus 50 C. Hence, this recently identified hydrate may be present there if
you had a highly salty lake, for example in Antarctica, that could be
exposed to these temperatures, Journaux added.
To enable a more extensive investigation and confirm that the signs from
ice moons match those from the recently found hydrates, the team intends to
either create or gather a bigger sample.
Jupiter Icy Moons Explorer from the European Space Agency and Europa
Clipper from NASA will both launch in April and October, respectively, to
investigate Jupiter's icy moons. Titan, a moon of Saturn, will be visited by
NASA's Dragonfly mission in 2026. It will be easier to focus their hunt for
signs of life if they are aware of the compounds that these missions may
encounter.
According to Journaux, these are the only planetary bodies (apart from
Earth) where liquid water remains stable throughout geological timeframes,
which is essential for the genesis and evolution of life. "They are, in my
opinion, the ideal location in our solar system to find alien life,
therefore we need to study their unusual interiors and seas to better
understand how they developed, evolved, and can maintain liquid water in
frigid areas of the solar system, so far from the sun."
