National Geographic
Menu

Exploring Uranus

Sometimes it seems like being large, distant, and gassy is a major turn-off for space engineers—unless you’ve got great eyes or lots of jewelry.

Of the eight recognized planets in our solar system, the terrestrial worlds are by far the in-crowd as far as scientific orbiters are concerned, with Mars and Earth as the obvious choices for prom king and queen.

beagle-crater.jpg

“Crown me!”

The Beagle Crater on Mars, as seen by the rover Opportunity in 2006

—Image courtesy NASA/JPL-Caltech/Cornell/UNM

Meanwhile, Jupiter with its Great Red Spot and Saturn with its mighty rings appear to be the only gas giants that have captured the attention of people who design probes to go study planets.

Granted, many robotic visitors to Jupiter have breezed past in a hurry, most recently the New Horizons probe that swung by in February 2007 on its way out to the Kuiper belt.

But the Galileo craft gave Jupiter seven good years in orbit, and a second orbiter named Juno is already in the works to launch in 2011.

Saturn has had Cassini since 2004, and that probe has just been showering the ringed world and its moons with affection.

saturn-eclipse.jpg

—Image courtesy NASA/JPL/Space Science Institute

Uranus and Neptune are left as the nerdy outcasts. Sure they both spent some time with the Voyager twins, but who in the outer solar system hasn’t?

At least Neptune has a proposal—rumors are spreading that NASA has said it will design a Cassini-esque mission for the distant giant, although word is that it’s a long and tenuous engagement.

Poor Uranus. After a narrow miss at being the only kid on the block to get a name like George, the planet earned official recognition as the butt of almost every astronomy joke made on national television.

Go ahead, snicker. It’s okay, he’s used to it.

uranus-voyager.jpg

—Image courtesy NASA/JPL/USGS

Every now and then, though, someone shows Uranus some serious attention, and last week it was the planet’s first love: a ground-based telescope.

The first planet discovered using a telescope, Uranus is an oddball when it comes to weather. The planet is tilted 98 degrees on its axis (nearly horizontal), so the sun shines directly on the north pole for about 20 years while the south pole is left in the dark, then vice versa.

Such long alternating periods of light and dark don’t actually affect things much, as Uranus is too far away from the sun for there to be a big difference between day and night temperatures. In general, it’s cold no matter what.

But the tilt does make it hard to get a good idea of what’s going on seasonally, especially since a Uranian year lasts for 84 Earth years. In other words, one day on Uranus is 42 years long, so watching things move from winter to spring is a bit of a challenge.

Luckily in 2007 the planet was aligned so that the sun was shining right on its equator, giving observers on Earth a peek at the northern and southern hemispheres at the same time.

Recently released images from the Keck II Observatory in Hawaii show how atmospheric changes on Uranus driven by the sun affect its cloud bands and other such features.

uranus-seasons.jpg

—Image courtesy W.M. Keck Observatory

One of the more interesting finds was that a unique vortex that appears to have been a regular feature on Uranus’s southern side for decades began drifting north in 2004, and could even be gone in coming years. Scientists attribute this change to the shifting seasons, but that’s just speculation for now.

So the question remains: Why is it that such an interesting planet and its family of moons can’t get an orbiting “date”? Hey, Uranus even has rings, too!

Distance and budget are surely concerns, but considering that there’s already two major probes—New Horizons and IBEX—heading right now to even farther reaches of the solar system, other factors must be involved.

If NASA and the world’s other space agencies are unwilling, maybe it’s time for the grassroots space race to look into planetary orbiters. Come on, people, who wants to be the first amateur astronomer to probe Uranus?