A LONELY spacecraft is
nearing Pluto after a three billion-mile journey lasting almost nine years.
NASA’S New Horizons probe awoke
from hibernation on December 6 and is preparing to explore the solar system’s
mysterious “ninth planet”.Discovered in 1930, Pluto was until recently described as the planet furthest from the Sun — an average distance of 3.67 billion miles.
In 2006 it was reclassified as a newly defined “dwarf planet” within the Kuiper Belt, a swarm of icy objects beyond the realm of true planets such as the Earth and Mars.
The Kuiper Belt is one of the last unexplored regions of the solar system along with the even more distant Oort Cloud, another band of icy bodies.
Both are thought to be the source of comets.
New Horizons will start observing the Pluto system on January 15.
It will make its closest approach to the dwarf planet on July 14 and by mid-May is expected to beam back images of Pluto and its moons better than any obtained by the Hubble Space Telescope.
Project scientist Hal Weaver, from the Applied Physics Laboratory at Johns Hopkins University in Maryland, US, said: “New Horizons is on a journey to a new class of planets we’ve never seen, in a place we’ve never been before.
“For decades we thought Pluto was this odd little body on the planetary outskirts; now we know it’s really a gateway to an entire region of new worlds in the Kuiper Belt, and New Horizons is going to provide the first close-up look at them.”
When New Horizons was brought out of hibernation 162 million miles from Pluto it was described as a “watershed event”.
Scientists received a signal telling them the probe’s pre-programmed computer had switched it to “active” mode that took four hours and 26 minutes to reach the Earth.
Since its launch on January 19, 2006, New Horizons has spent 1873 days — about two-thirds of its flight time — in hibernation to save wear and tear on electrical components and reduce the risk of system failures.
With thanks to The Australian
ONCE known as the ninth rock from the Sun, Pluto had its planetary
status downgraded nearly a decade ago to the less impressive “dwarf planet” or
“plutoid”.
Now the head of the first mission to Pluto, which begins scientific observations today, is mounting a campaign to have it reinstated to its rightful place.
Alan
Stern, the principal investigator of Nasa’s New Horizons mission, said: “I think
the public will discover it’s been a planet all along. When they see it close
up, they won’t know what else to call it.”Now the head of the first mission to Pluto, which begins scientific observations today, is mounting a campaign to have it reinstated to its rightful place.
Pluto’s demotion, by the International Astronomical Union shortly after New Horizons was launched in 2006, was a decision that Dr Stern considers “a gross mistake that is an embarrassment to astronomy”.
The $86 million mission finally officially begins its “encounter” with Pluto today, as it starts taking measurements of the solar wind and dust on the approach.
Later this month the spacecraft will begin sending back images of Pluto and its five moons to Earth. At first they will be used for navigation purposes to tweak the spacecraft’s trajectory if necessary. By May the images will exceed the best resolution images to date of Pluto, from the Hubble Space Telescope, which show a spherical mottled body, but reveal almost nothing about the appearance of the surface, its atmosphere or geology.
“In July we’ll have imagery so good that if we were flying over London we’d see the runways of the airports,” Dr Stern said. “It’s like the old days of space exploration when we went to Mars and everything was new. To turn a point of light into a planet within a matter of weeks is amazing.”
Andrew Coates, the head of planetary science at the Mullard Space Science Laboratory, said: “We know it’s spherical, but beyond that we don’t have any detail of surface features. There could be cliffs and geysers.”
The mission could also shed light on the planet’s “anti-greenhouse effect” where the atmosphere appears to get warmer higher up, the reverse of what happens on Earth.
The distance to Pluto — 5 billion km — means it will take New Horizons an hour to send back a single picture and more than a year to return all the data it accumulates during the fly-by.
Pluto is thought to be composed of about two thirds rock encased in a lot of ice, with surface temperatures of about minus 230C. Despite its bitterly cold surface temperatures, scientists believe that there could be a warmed liquid ocean beneath the ice, which could send plumes of nitrogen up from under the surface.
Dr Stern declined to make specific predictions about Pluto’s appearance, other than “we’ll find something wonderful”.
In July the probe will get to within about 10,000km of Pluto, and within 27,000km of Charon, its largest moon. The craft is travelling too fast (13km/s) and Pluto has insufficient gravity for it to go into orbit and so after its encounter New Horizons will speed out into the Kuiper belt, a zone of frozen rocks and asteroids that marks the outer solar system.
Hal Weaver, a New Horizons project scientist at Johns Hopkins University in Baltimore, said: “For decades we thought Pluto was this odd little body on the planetary outskirts; now we know it’s really a gateway to an entire region of new worlds in the Kuiper belt, and New Horizons is going to provide the first close-up look at them.”
The craft came out of hibernation last month — it has spent about 1,873 days in shutdown mode to save energy.
Thanks to the The Australian
