Written backwards, the story of the Hubble Space Telescope has echoes of Tennyson's epic narrative of the goingson a bit up-stream from Camelot:
The mirror crack'd from side to side;
"The curse has come upon me!" cried
The Lady of Shallott.
But now, the Hubble mirror all intact, fair science is, as it were, the youth of the Lady of Shallott revisited:
And moving thro' a mirror clear,
That hangs before her all the year
Shadows of the world appear.
And they are shadows not only of this world, but also of the next - our nearest neighbour, Mars.
The Hubble has watchers of the skies in a tizzy these days because of its series of pictures that show a large storm not too far from the Martian north pole. It is bigger than was thought possible on that planet, with an "eye" 200 miles across and comparable in size to the great depressions here on Earth, three times bigger than anything yet seen on Mars.
Although the Martian "year" is nearly two years long by our reckoning, the planet has distinct northern and southern seasons that are similar to those on Earth, because its rotation axis is tilted with respect to its orbital plane by about the same amount. But, unlike here on Earth, the southern and northern summers on Mars are very different from each other.
The Martian orbit around the sun is very elliptical, so the solar energy reaching the Martian surface during the southern summer, when the planet is closest to the sun, is about 40 per cent greater than it is in the northern summer when the planet is in the outermost segment of its path.
As a consequence, Martian southern summers are about 20C warmer than its northern summers; the northern summer is currently at its height.
The Martian atmosphere, composed almost entirely of carbon dioxide, is very much thinner than that of Earth, and the barometric pressure is correspondingly reduced. The frequent dust storms, which are a feature of the planet, normally last only a few days, and can be seen occasionally from Earth by telescope as bright spots on the reddish disc of Mars.
They occur when local winds reach speeds of over 100 m.p.h., but with its very flimsy atmosphere it takes a wind of that force on Mars to accomplish what a light breeze here on Earth can do so easily: raise a little dust.
The storm raging violently near the north pole at present, however, is particularly interesting in that it contains, not just dust, but water ice, just like the storm systems we experience here.