Readers discuss cloud formation, Stonehenge and Earth’s frenemy Jupiter

Icy moves

Stonehenge’s central stone, often often often called the Altar Stone, can have had Scottish and now no longer Welsh origins, researchers say. The finding suggests that Late Neolithic groups had long-distance connections, Bruce Bower reported in “Stonehenge’s roots extend to Scotland” (SN: 9/7/24 & 9/21/24, p. 10).

Reader Ralph Bradburd wondered if a glacier, now no longer humans, can don't have any longer lower than partly transported the Altar Stone from Scotland to southern England, where Stonehenge is found.

That scenario is worth allowing for but just seriously is not going to be going, says geoscientist Anthony Clarke of Curtin University in Perth, Australia. Ice sheet reconstructions show that glaciers moved northward from the Grampian Mountains in central Scotland toward the Orcadian Basin in the northeast, where the Altar Stone is believed to have come from, he says. So glacial movement up there would now no longer have brought the Altar Stone south to Stonehenge.

What’s more, there may also be little evidence of rocks deposited by glaciers, often often often called glacial erratics, in central southern Britain, Clarke says. And specifically, erratics from Scotland have now no longer been found near Stonehenge.

Up in the air

Cloud-forming aerosols will probably be forged the total way through stratospheric air intrusion events, wherein Earth’s jet streams cause stratospheric air to dip into the underlying troposphere, Carolyn Gramling reported in “Earth’s jet streams sow cloud seeds” (SN: 9/7/24 & 9/21/24, p. 12).

Reader James W. Benefiel asked whether it’s more likely for clouds to form when water vapor in the upper troposphere condenses on particles.

That is definitely a known mechanism for the formation of cloud condensation nuclei, the tiny particles that water droplets condense onto and that are the genesis of clouds, Gramling says. Such particles can form where convective clouds, equivalent to thunderstorm clouds, carry gases or tiny particles from Earth’s surface high into the atmosphere, where water vapor can condense onto them.

What this new find out about suggests is an absolutely different chemical process for cloud formation, which involves ozone from the stratosphere, Gramling says. Stratospheric air intrusion events were already a known phenomenon. Now researchers have linked such events to a bump in the formation of cloud condensation nuclei. The scientists propose that the integration of stratospheric ozone with tropospheric moisture, catalyzed by sunlight, may expand the production of free hydroxyl radicals, react with other molecules to create the cloud-forming particles.

Given the frequency of stratospheric air intrusion events, this mechanism will probably be a significant source of cloud nuclei, Gramling says. But just how a lot remains unknown.

Friend or foe?

A chemical analysis suggests that the asteroid that killed the dinosaurs came from beyond Jupiter, Carolyn Gramling reported in “Dinosaur killer’s origin revealed” (SN: 9/7/24 & 9/21/24, p. 7).

The story sparked a energetic discussion on Reddit about whether Jupiter shields Earth from asteroid and comet collisions.

Reddit user DonManuel wrote that Jupiter’s failure to give protection to Earth from the dino-killer shows “how important the protection of Jupiter in point of fact is for life on Earth.” But user Astromike23 wrote that the premise that Jupiter shields Earth from impacts is a myth.

Indeed, Jupiter’s role as a planetary protector is now no longer so clear-cut. The planet’s immense gravitational pull can influence the orbits of nearby objects, which is most often a double-edged sword for Earth.

Some studies suggest Jupiter may defend Earth and neighboring planets from impacts by pulling passing asteroids and comets toward itself or flinging them out of the solar system entirely. But other research suggests Jupiter may slingshot asteroids and comets into the inner solar system and set up a collision course with Earth or its neighbors. Jupiter may attract objects that wouldn’t in most cases pass Earth, increasing the likelihood for collision.