NEW HORIZON MISSION HAS CHANGED OUR IDEAS ON PLUTO

 NEW HORIZON MISSION HAS CHANGED OUR IDEAS ON PLUTO

Nikunja Bihari Sahu

      From a small, distant, faint point of light in 1930 (ever since it was discovered by the US astronomer Clyde Tombaugh) to the recent rendezvous of  NASA’s New Horizon Flyby Mission, the dwarf planet  Pluto has evoked many speculations during in  its 85 years of  history. The mission has completely revamped our ideas on this mysterious world   and shown us a world in great detail like never before. It is going to be a fascinating new world now with immense surface features and hectic geological activity! Some of the  landmark findings of the mission is outlined below:

 An active world with tall mountains  

The high-resolution close-up photograph of Pluto's surface revealed a bizarre craterless surface unlike most Solar System planets and their Moons. Planetary craters are generally formed by the bombardment of meteors or asteroids from space over time. It is thought that the craterless planets like Earth, Venus and Mars might have had some craters in past, but were covered with new terrain in course of time due to intense geological activity like earthquakes or Volcanic eruptions taking place periodically on them.

     Based on the lack of craters in Pluto, scientists estimate its surface to be hardly 100 million years old — rather geologically young compared with the 4.5 billion years since Pluto originally formed. It has also surprisingly large icy mountains (one of which measures 11,000 feet tall even higher than the Rockies). This suggests hectic geological activity taking place in the interior of Pluto. But the question is: What heat source could be fueling this activity on such an icy world?

        On some planets (including our Earth), the slow decay of the radioactive material (that formed since its origin) provides heat. But these are the bodies much larger than Pluto and it should not have enough radioactive material by now for this process to still going on. For some smaller bodies like the Jupiter’s Moon Europa, the heat is produced by a phenomenon called the Tidal Effect in which a smaller body ( like Europa) is squeezed by the gravity of the larger body (like Jupiter). But it is unlikely that this effect is happening in Pluto as there is not anything big around it to gravitationally squeeze it.   Scientists are now speculating that   a sub-surface ocean that is gradually freezing over time is releasing heat into the crust   or the surface ice is acting as a blanket slowing down the rate of heat escaping to space.

 Pluto is slightly bigger than previously thought

   Because Pluto has a thin envelope of atmosphere, it gives a hazy edge to its appearance that hinders precise measurement of its size from a far away distance. But as the New Horizons closed in before the flyby, it allowed scientists to have a close look at the dwarf planet from a close proximity and measured its diameter to be 1,473 miles with unprecedented accuracy 

     This figure is especially interesting; because it means Pluto is slightly larger than another dwarf planet Eris ( with 1,445 miles in diameter) which was earlier believed to be larger than Pluto since its discovery in  2005 that eventually heralded the  controversial decision  by International Astronomy Union ( IAU) to officially degrade Pluto from its rank  as a Planet to a Dwarf planet. Supporters of the decision argued that Pluto was merely one of many similar objects in the Kuiper Belt, the region of space beyond Neptune that is filled with chunks of rock and ice. But the new finding excites Pluto lovers of the idea that Pluto should be a planet because of the largest known Kuiper Belt object.

 Pluto is Reddish brown in Colour

 

    Scientists first got the scope of looking at the colourful Pluto way back in 2002 through the spectacular images of the Hubble Space Telescope.  But as New Horizons closed in, its Ralph Imager  instrument captured detailed colour photograph confirming that the dwarf planet has indeed a characteristic colour and it is reddish brown. Scientists are now suggesting a possible explanation for this unusual hue of the dwarf planet.

    The reddish-brown color is likely the result of the interactions between Methane molecules in Pluto's atmosphere and the Ultraviolet rays emitted by the Sun and distant Galaxies. When these rays hit Methane molecules, it triggers the formation of a solid Hydrocarbon compound called Tholins which is reddish brown in color. Scientists have verified the correctness of their hypothesis by simulating similar chemical processes in their labs on Earth. The same phenomenon has also been observed on Saturn's moon Titan and Neptune's moon Triton.

 Pluto has ice caps 

    Scientists long believed that Pluto had ice caps, but measurements taken by New Horizons just prior to its flyby confirmed that the ice caps do really exist and these are actually made of Methane and Nitrogen. What's really intriguing is that these ice caps look very different at different times of the Pluto’s year. Pluto's distance from the Sun varies greatly during its annual journey around the Sun which is 248 years and, at some time, it's even closer than Neptune. Scientists believe that during Summer, some of this ice turns into atmospheric gas through a process called sublimation and during Winter, these gases fall back to the ground as snow. As Pluto is in late Summer right now, the Snow is likely to begin falling that would continue for many decades from now. 

 Pluto’s  Nitrogen atmosphere is fast evaporating  

        As New Horizons approached Pluto, its PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) instrument sniffed space for particles escaping from its atmosphere and it found atoms of Nitrogen do really exist at a distance of 7 times the Pluto's radius.  We knew that gases steadily escape Pluto's atmosphere as part of a usual process called Hydrodynamic outflow, but finding any sort of escaping particles at that greater distance suggests that Pluto is losing its atmosphere at a rate faster than previously thought. Earth is also believed to have gone through the same process billions of years ago. This rids our planet of its early toxic Hydrogen atmosphere and allowed Nitrogen and Carbon dioxide to build up eventually giving rise to life.

The Moon Charon is more complicated than thought

                 During the flyby, New Horizons also had a look at the planet’s 5 moons (Including the largest Moon Charon) and collected images. For years, scientists thought of Charon as a bald featureless ball of ice and rock, but the recent images have proved the idea wrong. The images revealed the Moon is actually covered with cliffs, troughs, and canyons (some may even be deeper than the Grand Canyon on Earth). The Moon has fewer craters than anticipated, raising the possibility of geologic activity there too. The Moon also has a large, mysterious dark spot at its top which is a complete surprise for the scientists. It may be simply a large impact basin formed by some collisions long ago or could be the result of gases ejected from Pluto over time. 

 

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                                                                                                                                                    Reguonal Science Centre

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