A new study reveals a curious connection between Saturn’s moon Rhea and its neighbor Titan.
The second largest the planet of the solar system, Saturn is adorned with ice rings and an orbit of a real swarm of about 80 moons.
These satellites have their own unique properties, some so unusual and intriguing that they stand out from other lunar bodies found in the solar system, including our own natural satellite, the Moon.
One of these strange celestial bodies is Saturn’s second largest moon, Rhea. The moon can be a cold, airless object, but it also has three narrow, dense rings ̵
And now, Cassini’s old data may solve this long-standing lunar mystery.
The new findings are described in detail in a study published Friday in the journal Scientific progress.
Here is the background – Rhea is the second largest moon in orbit around Saturn – with a radius of 475 miles. The moon is locked around Saturn for a week, which means that one side of Rhea is constantly facing the big planet. It completes the entire orbit of the gas giant in 4.5 Earth days.
Rhea is a cold, harsh world. Its temperatures range from -281 degrees Fahrenheit in sunny areas to -364 degrees Fahrenheit on its dark side. In accordance with the low temperatures, the moon is largely composed of water ice.
The mystery of Rhea’s surface began decades ago when NASA’s Cassini spacecraft flew from Rhea as part of its mission to explore Saturn and its moons. Cassini performed spectrographic analysis, collecting ultraviolet images of the moon and its chemical composition, confirming that its surface is composed of ice. But the data also show evidence of unidentifiable material.
3D model of the moon of Saturn, Rhea, made by applications and development of NASA visualization technology.
How did you do it – Bhalamurugan Sivaraman is an associate professor at the Physical Research Laboratory in India and co-author of the new study. He says Back his team tried to study the chemical nature of this mysterious signal. To do this, the team turned to Cassini’s initial data.
“We used data from Cassini’s archive to find out exactly what was going on,” Sivaraman said..
The team re-analyzed data collected by one of Cassini’s Rhea flies and conducted experiments here on Earth to see if they could identify the chemical composition of the molecules that produce the unknown absorption band.
The team behind the new study is analyzing data collected from Cassini’s Rhea flyover and conducting laboratory experiments to test different molecules and see which one would produce the unknown signal.
What they found – Tracking possible candidates, the researchers eventually hit the probable culprit: hydrazine. This is the first time the compound has ever been discovered on the moon, according to the study.
“When we did the hydrazine experiment, it was a coincidence,” says Sivaraman.
Hydrazine is an inorganic compound, a colorless liquid with the same pungent odor as ammonia. Here on Earth it is used in pharmaceuticals, agrochemicals and as a fuel for spacecraft.
To find out where hydrazine might come from, Sivaraman and his colleagues essentially tried to recreate Rhea’s surface conditions in the lab.
Interestingly, these simulations suggest that Rhea’s lunar neighbor, Titan, Saturn’s largest moon, may be linked to the presence of hydrazine. Titanium can emit nitrogen molecules to Rhea, which then interacts with moon radiation to turn nitrogen into hydrazine, the researchers suggest.
This type of interaction between two moons is rare in our solar system. But given how large Titan is, the moon is likely to have some impact on its surrounding objects, Sivaraman explains.
What next – Given that this is the first discovery of hydrazine on the moon, the team behind the study wants to continue observing other moons to see if hydrazine forms elsewhere in the solar system. They also suspect that there may be as yet unknown chemistry that is also waiting to be discovered.
“This particular work helps us identify another molecule that we didn’t know existed before,” Sivaraman said.
“We would like to look for molecules that are absorbed at other wavelengths.”
Summary: We present the first analysis of the long-range ultraviolet reflection spectra of the regions of the leading and subsequent hemispheres of Rhea collected by the Cassini Ultraviolet Spectrograph during target flights. In particular, we seek to explain the unidentified broad absorption characteristic centered near 184 nm. We used laboratory measurements of ultraviolet spectroscopy on a set of candidate molecules and found appropriate adaptation to the Raya spectra with both hydrazine monohydrate and several chlorine-containing molecules. Given the radiation-dominated chemistry of the surface of the ice satellites embedded in the magnetospheres of their planets, hydrazine monohydrate is said to be the most plausible candidate for explaining the absorption characteristic at 184 nm. Hydrazine was also used as a fuel in Cassini propulsion systems, but the propulsion devices were not used during ice satellite flights and thus the signal is not thought to originate from spacecraft fuel. We discuss how hydrazine monohydrate can be chemically produced on icy surfaces.