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By Rajib Sen

NASA reaches Pluto with a Flyby

Pluto is the last of the original nine planets never to have been explored by mankind. Spacecraft made on Earth have visited Venus and Mars in the 1960s, Mercury, Jupiter and Saturn in the 70s and, in the 80s, Uranus and Neptune. Only Pluto demoted to a dwarf planet, remained. Till 15 July 2015 – when New Horizons reached within 7,750 miles, a distance less than the Earth’s diameter and closer than Pluto’s closest moon.
In fact, if Earth is reduced to the size of a basketball, Pluto would be no bigger than a golf ball – it would have to be 50 to 80 miles away (depending on the orbit at any given time). Also, it is startling to realise that the last time when Pluto was in its present position was in 1768 – when people had no idea of aviation, and spaceflight wasn’t even dreamt of! Launched by NASA from Cape Canaveral in 2006, it was precisely timed in such a way that it took the shortest time in the shortest distance to reach Pluto which makes an elliptical 248-year orbit around the sun. Thus, thanks to a booster from the gravity of planet Jupiter around which it was slung, the intrepid spacecraft, barely the size of a concert grand piano and shaped like it, took 3,463 days (over nine years) to cover the 2.97 billion-mile journey – as much as the distance between Earth and the sun multiplied by 32! And New Horizons is the fastest spacecraft ever built zooming ahead at 30,000 miles per hour on an Atlas V rocket, seeking the new horizons for which it has been named.
In fact, New Horizons was launched while Pluto a few months before Pluto’s planetary designation was downgraded to that of a plutoid or dwarf-planet and officially just ‘asteroid No. 134340’. This is the globe that was discovered in 1930 by a young American scientist Clyde Tombaugh, who died on 17 January 1997 – nine years and two days before New Horizon’s launch – and whose ashes are being carried by New Horizons to the planet which got its name in a competition won by Venetia Burney (then 11 years old) who was paid the princely sum of five pounds! New Horizons’ amazing pictures have revealed for the first time that Pluto is as red as Mars, Earth’s nearest neighbour. That is far removed from the dark, icy world that was expected. The first close-up shots sent back in fact showed a rusty tint, a Mars-like colour, and the strange, heart-shaped element that is already the dwarf-planet’s Internet identity.
From the photos taken by New Horizon’s Long Range Reconnaissance Imager, scientists have determined that Pluto has a diameter of 1,474 miles, a bit bigger that had been thought earlier. But that also confirms that Pluto is larger than any other known object in our solar system beyond the orbit of the farthest official planet, Neptune.
These photos reveal ice mountains of up to 11,000 feet high and canyons that are up to six miles deep on Pluto’s biggest moon, Charon. A paucity of craters indicates that, in the recent past, both objects have been active geologically. Close-ups of Pluto revealed a vast, craterless young plain possibly still undergoing geographical development that has been named Sputnik Planum after the world’s first artificial satellite sent aloft by the old Soviet Union on 4 October 1957. There is also a frozen region just centre-left of the heart-shaped feature in the icy north that has been informally been named “Tombaugh Regio” after the discoverer of Pluto. This has “exceeded all pre-flyby expectations,” the scientists noted.
Elsewhere, NASA says the surface seems etched by fields of small pits that may have formed from the sublimation process in which solid ice turns directly into gas. Another preliminary finding is dark streaks on the icy plains that might have been produced by the high winds blowing across the frozen surface. New Horizons also indicated that Pluto’s nitrogen-rich atmosphere could be quite extensive.

The New Horizons Particles and Plasma team has fund a region of cold, dense iodised gas tens of thousands of miles beyond Pluto’s atmosphere at an altitude of over 170 miles above its surface. NASA says that the atmosphere is being stripped away by solar winds.

“We are already seeing complex and nuanced surfaces that tell us of the history… that is beyond our wildest dreams on the science team,” the mission’s principal investigator, Alan Stern, enthused. “It feels good. So many people put so much work into this around the country. It’s a moment of celebration. We have completed the initial reconnaissance of the Solar System, started under President Kennedy.”

Fifty-four years ago, on 25 May 1961, barely four months as president of the US, John Fitzgerald Kennedy proposed before a joint session of Congress that “this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth.” They not only did that but soared beyond to reach Pluto now.
The spacecraft whooshing past Pluto at some 31,000 miles an hour just can’t be slowed down. So the flyby must collect whatever data it can in an incredibly small window of time before shooting off to its next horizon – the Kuiper Belt of icy worlds that ring the outer solar system. With a download speed of only two kilobytes a second and the signals taking a good four hours to reach Earth, most of the data being gathered by New Horizons will take at least another 18 months.
Now, scientists must wait. It takes some 4.5 hours for whatever data the spacecraft transmits to reach Earth with a very dim signal. Thus, NASA has resorted to three 200-foot-wide radio dish antennas positioned in Australia, Spain and California to take care of the terribly low, one kilobit/second rate of transmission – by which a 1024-pixel-wide image will take over 42 minutes to reach Earth from the spacecraft.
That is how, after 21 hours of high suspense, scientists were relieved by New Horizons’ farewell phone call sent 13 hours after the Pluto flyby. Thereafter, the spacecraft ceased to send anything to mission control because its antennas had been turned away.
“After nearly 15 years of planning, building, and flying the New Horizons spacecraft across the solar system, we’ve reached our goal,” said project manager Glen Fountain at the Johns Hopkins University Applied Physical Laboratory in Laurel, Maryland, which designed, built and operates New Horizons for NASA. “The bounty of what we’ve collected is about to unfold.”