Readers discuss Mimas’ hidden ocean and ancient cave art

Hidden depths

Slight changes in the orbit of Saturn’s moon Mimas hint at the presence of a vast, young ocean beneath the satellite’s icy surface that may have formed between 5 million and 50 million years ago, Adam Mann reported in “This Saturn moon may harbor water” (SN: 3/9/24, p. 8).

Reader Bobby Baum asked how the ocean formed so recently and whether an ocean could have formed multiple times in the past.

Saturn’s moons gravitationally interact with one another and with their ringed parent planet as they orbit. This complex dance causes tidal stresses on the moons, generating heat that can melt a satellite’s icy interior.

The putative ocean beneath Mimas’ surface probably formed because of such an interaction with at least one of the other Saturnian moons in the recent past, says Valéry Lainey, an astronomer at the Paris Observatory. “We do not know yet which [other] moon is responsible for this, but such interactions are very common in celestial mechanics,” Lainey says.

The subsurface ocean probably didn’t exist earlier in Mimas’ history, Lainey and colleagues suspect. That’s because the team has not seen any evidence of surface deformations that a thick, liquid ocean would have caused.

Kids’ creations?

Radiocarbon dating suggests that ancient cave paintings in Argentina are nearly 8,200 years old. That age implies that the region’s rock art tradition, which probably preserved cultural knowledge shared by hunter-gatherers, is several millennia older than previous evidence suggests, Bruce Bower reported in “Patagonian cave kept culture alive” (SN: 3/9/24, p. 16).

Reader Joan wondered if children, rather than adults, could have created the ancient art. “I often had my children draw and paint when they could not play outside. If I was stuck in a cave with my children, they would have been painting on the walls,” Joan wrote.

“There is no way to know for sure who made these cave paintings,” Bower says. Some researchers have long suspected that Stone Age children and teenagers used their fingers to impress line patterns on cave walls, as well as leave behind kid- and teen-sized hand stencils inside caves (SN: 4/28/07, p. 264). “If young people made some or all of the cave paintings in Argentina, they participated in what may have been a system for transmitting cultural knowledge that lasted over 3,000 years,” Bower says.