Phoenix snapped its first picture of ice (white surface) directly underneath the belly of the lander soon after a perfect touchdown on 25 May on Mars鈥檚 northern plains. 鈥淚f you had a broom, you could make an ice-rink right where we landed,鈥� said mission chief Peter Smith
The solar system came into unprecedented focus in 2008. Various spacecraft revealed previously unseen swathes of Mercury, found a ring around one of Saturn鈥檚 moons, and landed squarely on a patch of Martian ice.
Despite nervous peanut shelling by team members on Earth, NASA鈥檚 Phoenix lander made a flawless touchdown on the Red Planet on 25 May.
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The lander lasted more than five months on the surface, before it was hobbled by a lack of Sun. But in the probe鈥檚 short lifetime, Phoenix revealed unexpectedly small polygons on the surface, soil alkaline enough to grow turnips in, a chemical never before seen on Mars, and direct evidence of water ice that had been predicted to lie near the planet鈥檚 surface.
Dust storms
Not to be outdone, the Mars Reconnaissance Orbiter found what may be vast underground ice glaciers near the equator as well as widespread opal deposits, suggesting liquid water persisted for longer on the planet than previously suspected. The probe also found rock outcrops containing carbonates, suggesting the water that formed them about 3.5 billion years ago might have been less acidic and more hospitable to life than originally thought.
The news was less positive for NASA鈥檚 Mars Science Laboratory. The SUV-sized, nuclear-powered rover has unresolved technical problems that will force it to launch in 2011, two years later than planned. The delay will add $400 million to the mission and could force NASA to postpone another major planetary mission.
Meanwhile, the twin Mars rovers have refused to die after five years on the Red Planet, although a dust storm caused Spirit鈥檚 power levels to drop to an all-time low in November.
For the first time, sky watchers found a space rock on a certain collision course with Earth. Fortunately, it was too small to do any damage, hitting the atmosphere above northern Sudan a day after it was spotted.
Spider scar
NASA鈥檚 Messenger spacecraft finished two flybys of Mercury, photographing 50% of the planet that had never been seen before by spacecraft. The probe revealed a mysterious spider scar and strange blue patches, as well as further evidence that the planet has a fluid core and has shrunk over time.
Some modellers also predicted that instabilities in Mercury鈥檚 orbit could send the planet careening through space in 5 billion years or so, prompting the Earth to collide with Mercury or Mars.
Beyond the asteroid belt, NASA鈥檚 Cassini probe found a ring around Saturn鈥檚 moon Rhea, making it the first moon known to host its own debris ring.
Cassini also made three flybys of Saturn鈥檚 moon Enceladus to taste and image giant plumes of water vapour and ice that extend hundreds of kilometres from the moon鈥檚 surface. The energy source for these plumes is still being debated, but high-speed jets within the plume may point to a reservoir of liquid water 鈥� which might be hospitable to life 鈥� beneath the surface.
Alien comet?
Cassini also revealed evidence that Enceladus has a comet-like composition, which is puzzling since the moon is thought to have formed closer to the Sun than comets.
Elsewhere in the solar system, a third red spot erupted on Jupiter, only to be torn apart by its siblings less than three months later.
Astronomers found an object in the distant Kuiper belt that seems to orbit the Sun backwards, caught a glimpse of the first peanut-shaped comet and puzzled over the chemical signature of a comet that may have come from another planetary system.
The Deep Impact spacecraft, which sent a probe crashing into a comet in 2005 and is now searching for extrasolar planets, was used in the first test of an interplanetary internet that could streamline the way data is sent between spacecraft and Earth. The probe also imaged Earth from 50 million km away, revealing what alien astronomers with telescopes far more powerful than our own might see when they look at our home planet.
Celestial spectacle
Back on Earth, astronomers continued to debate whether Pluto should be considered a planet. The International Astronomical Union (IAU), which demoted Pluto to 鈥榙warf planet鈥� status in 2006, said Pluto and objects like it should be called 鈥榩濒耻迟辞颈诲蝉鈥�, a term one astronomer said sounded like 鈥榟emorrhoids鈥�.
The Sun, whose face had been virtually free of spots most of the year, entered a new cycle, though astronomers are divided over how active 鈥� and potentially damaging to satellites and power grids 鈥� this cycle will be.
The Sun was also the star of a total solar eclipse on 1 August. Watch what the event looked like from China.
Other notable sky events in 2008 included a rare conjunction of Venus, Jupiter and the Moon, a full Moon that shone about 30% brighter in December than at other times in the year because the Moon was about as close as it ever comes to Earth, and a 鈥榝ireball鈥� that not only lit up the skies above Canada but also left behind dozens of fresh meteorites that scientists and meteorite hunters rushed to recover.
