New Horizons Closes in on Pluto
When Clyde Tombaugh discovered Pluto in 1930 he could never have imagined that the icy world would one day be his final resting place. But this week Nasa’s New Horizons probe will arrive at the dwarf-planet carrying the astronomer’s ashes.
The mission aims to answer fundamental questions about the ninth rock from the Sun and will send back the first close-up pictures of our elusive neighbour. It could even help explain the origin of life on Earth. Tombaugh died on Jan 17 1997, nine years and two days before New Horizons’ launch, but one of his final requests was for his ashes to be sent into space.
A small container carrying his remains is fixed to the inside of the upper deck of the probe and bears the inscription, “Interned herein are remains of American Clyde W Tombaugh, discoverer of Pluto and the solar system’s ‘third zone’.”
Since Tombaugh discovered Pluto it has proved one of the most contentious subjects of the Solar System, with astronomers divided as to whether it is a planet, a dwarf-planet, an escaped moon of Neptune or even a comet.
New Horizons will be close enough to begin observing Pluto and its moon Charon and will begin a slow fly-past in the summer.
Its seven-instrument payload includes advanced imaging infrared and ultraviolet spectrometers, a compact colour camera, a high-resolution telescopic camera, two powerful particle spectrometers and a space-dust detector.“New Horizons is incredibly important,” said Dr Sheila Kanani, a planetary scientist at the Royal Astronomical Society, “because it is so far away we don’t know much about Pluto and Charon. We have a few pictures of Pluto but they are pixilated and fuzzy so we have high hopes from the images that New Horizons will give us. Pluto is made of rock and ice and has five moons, although the classification is still under debate. Its temperature is about -230C and Pluto is unusual in that as you go up in the atmosphere it actually gets warmer.
“But all these observations have taken place from the confines of Earth or images from the Hubble Space Telescope so it will be incredible to have data from the New Horizons mission — who knows what Pluto has to offer?”
The dwarf-planet, which is not even two-thirds the diameter of the Moon, is a member of the Kuiper Belt, a giant band of planetary debris left over from the solar system’s formation 4.56 billion years ago.
Because of its elliptical 248-year orbit, the mission has been timed so that the probe needed only travel the shortest possible distance. Pluto is currently 2.6 billion miles from Earth but at the furthest point of its orbit it can be 4.6 billion miles away.
The probe has spent 1,873 days in standby to save energy and was ’woken’ by Nasa on December 6 for the final leg of its journey.
“This is a watershed event that signals the end of New Horizons crossing of a vast ocean of space to the very frontier of our solar system, and the beginning of the mission’s primary objective,” said Alan Stern, New Horizons principal investigator from Southwest Research Institute in Boulder, Colorado.The spaceship will be closest to the dwarf-planet on July 14, near enough for images that will ‘knock your socks off’, promised Will Grundy, a mission team member and astronomer at Lowell Observatory in Arizona, where Pluto was first seen.
Dr Grundy believes that material from the Kuiper belt might have delivered organic molecules that sparked life on Earth.
“There’s no doubt that complex organic molecules do exist in the outer solar system, which were created via energetic radiation acting on simpler molecules,” Dr Grundy told Forbes magazine. “Whether they played an important role in seeding life on Earth is not yet known. It’s entirely possible that we didn’t need that stuff. But it’s equally possible that after the Earth had been sterilised and cooked and things cooled down, impactors from the outer solar system delivered key astrobiological ingredients.”
The astrophysicists will also be looking out for huge wind-swept dunes of ice and soot on the surface of the dwarf planet, which would prove that Pluto’s atmosphere was once much thicker.
Dr Kanani said space had recaptured the public’s imagination. “With new technology we have entered a new space age,” she said. “We are able to send satellites to comets and dwarf-planets and we are learning more about where we live and where we come from every day. We are able to observe planets for 10 years, which means our knowledge of the Solar System has increased a huge amount in the last 50 years.
“Twitter and Facebook, and other Internet sharing sites, means that the whole world can connect and celebrate the wonderful science, engineering, technology and maths that is being done across the world, and across the Solar System, today.”