This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Saturn's icy moon Enceladus hides a global ocean beneath its frozen surface. From fractures near its south pole, material from this ocean is ejected into space as a plume of water vapor and ice particles.
These particles offer scientists a rare opportunity to investigate an extraterrestrial ocean without drilling through kilometers of ice. Now, an international research team including scientists from the Earth-Life Science Institute (ELSI) at the Institute of Science Tokyo has uncovered how ocean water may be transformed on its journey from the subsurface ocean into the tiny ice grains observed in space. The research is published in the journal Science Advances.
From 2004 to 2017, the Cosmic Dust Analyzer aboard the Cassini spacecraft measured the composition of individual ice grains in Saturn's E-ring, which is supplied by material ejected from Enceladus. Researchers led by professor Frank Postberg at Freie Universität Berlin analyzed 961 mass spectra of salt-rich grains, known as Type 3 particles. Rather than finding grains with broadly similar mixtures of ocean salts, they discovered striking chemical diversity.
Different grains were enriched in different salts, including sodium chloride, carbonates, phosphates and potassium chloride. In particular, chloride and carbonate were rarely found together in the same sodium-rich grain. This raised a question: If these particles originated from the same ocean, how did their compositions become so different?
To investigate, professor Yasuhito Sekine and colleagues at ELSI conducted laboratory experiments using droplets designed to reproduce the major salt components expected in Enceladus' ocean. The team froze droplets of different sizes at different cooling rates and examined how their constituent elements were distributed after freezing. The experiments revealed that cooling rate matters.
In droplets around 200 micrometers across, salts became spatially separated when the droplets froze slowly, at approximately 10 K per minute or less. Faster freezing produced a much more uniform distribution. "What surprised us was that the diversity seen by Cassini could emerge from droplets originating from essentially the same ocean water," said Sekine.
Extract — continue reading at the source.
