Proposed beginning
The Great Red Spot
A lid over a possible start — not a planet in the clouds
Jupiter’s longest-lived large storm. If a new world is starting, it would sit under this weather, not in the clouds we can see.
What is measured
It is the longest-lived anticyclone we know. A 2024 reconstruction finds the present Spot clearly recorded from 1831 and unlikely to be Cassini’s 1665–1713 Permanent Spot.
The long axis has shrunk from about 39,000 km in 1879 to about 14,000 km now, and the oval has grown rounder. A ~90-day wobble sits on top of that slow shrink.
As it contracted, cloud-top work found it a little taller and redder. That is a change in the weather layer’s shape, not a weighing of rock. That Hubble result was posted in the 2018 archive.
Juno, Hubble, and JWST put a deep, thermally odd vortex. The fitted floor is still around 100 bars — still Jupiter’s weather, not a rocky depth.
What is claimed — and what is not
The live claim is a prediction: extra mass should show up below that 100-bar floor, separate from the winds that already explain the storm.
Older pages on this site put a molten Earth in the clouds. That wording is withdrawn. It remains in the archive.
If later gravity or microwave maps show a storm that is only air, this beginning comes off the table.
The test
If the storm is only air all the way down, with no extra mass under the weather, this beginning comes off the table.
If the published shrink of about 200 km a year held, the long axis would fall below 10,000 km by the mid-2040s. Other work says the storm may instead lock to the winds around it. If it stays near 14,000 km, that calendar dies. Only extra mass under 100 bars remains as the test.