Astronomy
An Earth-sized storm on Jupiter known as the Great Red Spot may be a recent addition
JUPITER’S Great Red Spot could be younger than many astronomers thought. It is commonly accepted that the enormous storm was first observed by Giovanni Cassini in 1665, but it turns out that the spot he saw was probably different to the vortex visible now.
The spot, a storm larger than Earth, has been continuously observable since 1831. But an enormous storm was also visible at the same location on Jupiter from 1665 to 1713, and astronomers have been debating whether the two tempests are in fact one and the same for decades.
Agustín Sánchez-Lavega at the University of the Basque Country in Spain and his colleagues performed a systematic review and analysis of all the available observations of the earlier storm – which was known as the Permanent Spot – preserved in astronomers’ drawings.
They then compared them to early photographs and newer images of the Great Red Spot we see today. They found that, if the drawings are accurate, the Permanent Spot was far smaller than the Great Red Spot – its diameter would have had to grow at a rate of about 160 kilometres per year from 1713 to 1879 for the two to be consistent.
But none of Jupiter’s vortices have been shown to grow in such a rapid and sustained manner. Moreover, recent observations show that the Great Red Spot appears to be shrinking, not growing. This and other factors, along with the 118-year gap in observations, led the researchers to conclude that the two spots aren’t the same (Geophysical Research Letters, doi.org/m446). However, Scott Bolton at the Southwest Research Institute in Texas says it is difficult to make secure conclusions based on hand-drawn pictures of a distant world.
