Pluto: A mountainous, flat, frozen, and diverse world
Mountains, plains, glaciers, a wispy atmosphere, and substantial color variation have appeared in images of Pluto captured by NASA鈥檚 New Horizons probe.聽
As the spacecraft has sent data back to Earth over the past couple months researchers have been dazzled by the spectacular images. This week scientists summarize their findings in a new paper.
Scientists on NASA鈥檚 New Horizons mission published their on the Pluto system Thursday in聽Science.
鈥淧luto is a really interesting and geologically complex world,鈥� Cathy Olkin, deputy project scientist on the mission, told 海角大神 in an interview. 鈥淚t鈥檚 that diversity across this world that just makes it fascinating.鈥�
The paper discusses a variety of findings on the data received from New Horizons thus far. The spacecraft captured a trove of data during its historic flyby in July and will continue to send data back to Earth for about a year.
Exotic ices and water ice
Researchers spotted mountains reaching as tall as the Rockies, says Dr. Olkin. And those mountains may contain water-ice.
Previous spectroscopic studies of the dwarf planet revealed the presence of nitrogen, carbon monoxide and methane ices. But 鈥渢hose would be too soft to retain the sharp shape that we have on those mountains on Pluto,鈥� Olkin says.聽
Instead, water-ice must be present in a sort of bedrock on the planet. Thus, 鈥渢he observed N2, CO, and CH4 ices must only be a surface veneer above this bedrock,鈥� the researchers write in the Science paper.
That 鈥渧eneer鈥� may form part of one of the most distinct features on Pluto: the heart.
During New Horizons鈥� approach to Pluto, the spacecraft captured a picture that appeared to show a heart-shaped feature on the dwarf planet. Now called Tombaugh Regio, the region is bright, highly reflective and contains seemingly flat plains.聽
Those plains, forming the western half of the heart, have been dubbed Sputnik Planum.聽
And right smack dab in Sputnik Planum is a large glacier.
鈥淥n Earth we have glaciers,鈥� Olkin says. 鈥淥n Pluto there are glaciers, but they鈥檙e very different types of glaciers.鈥澛�
Pluto鈥檚 glaciers seem to made of exotic ices, like frozen carbon monoxide, methane, and nitrogen.聽
鈥淎 lot of that difference is driven by the temperature,鈥� Olkin explains. 鈥淧luto鈥檚 surface temperature is approximately -390 degrees Fahrenheit.鈥�
Characteristic of glaciers is their ability to slide, slowly. 鈥淲ater ice wouldn鈥檛 flow at the temperatures of Pluto,鈥� Olkin says. But the softer exotic ices would.
The researchers also spotted cellular, polygonal shapes in the ice. 鈥淭he question is, what is causing those shapes,鈥� says Olkin. The dominant idea is convection, with deep heat pushing at the ice from beneath.
Olkin describes it like cooking oatmeal. The heat underneath the pot will cause upwellings in the oatmeal. 鈥淚t can make patterns sort of like we鈥檙e seeing in the ice,鈥� she explains. So, perhaps there鈥檚 heat beneath the surface of Pluto.
A history of bombardment, active geological processes
A resident of the Kuiper Belt, a distant region of our solar system containing many comets, asteroids and other small, icy space objects, Pluto has likely encountered other small celestial bodies.聽
The researchers looked at the frequency and distribution of impact craters across the dwarf planet, compared with estimates of bombardment from the Kuiper Belt.聽
Based on the frequency of impact craters, they determined that other terrain-shaping processes must have been quite active within the past few hundred million years too. And Pluto鈥檚 surface could still be undergoing such changes, the scientists write in their paper.
鈥淪uch resurfacing can occur via surficial erosion/deposition (as at Titan), crater relaxation (as at Enceladus), crustal recycling or tectonism (as at Europa), or some combination of these processes,鈥� they write.
Stunning color on the dwarf planet
Much like Earth, Pluto has a blue sky. That color comes from molecules that scatter light in blue wavelengths. Tholins, the complex organic molecules, also give color to other aspects of the dwarf planet.
Those same particles may fall to the surface of Pluto, making the dwarf planet red. Tholins are actually a range of reddish colors. The blue hue of Pluto鈥檚 sky comes from the way they scatter light in the atmosphere.
A blurry speck turned spectacular world
The discovery of Pluto was the result of a early in the 20th century. Astronomers noticed that the orbits of Uranus and Neptune were a bit irregular, possibly caused by another significant celestial body.聽
Although Pluto was first photographed in 1915, researchers did not recognize the object for what it was. They expected to see a brighter object than the faint speck that was the dwarf planet.
When Clyde Tombaugh finally confirmed Pluto鈥檚 existence in 1930, it was named by 11-year-old Venetia Burney. Named after the Roman god to the underworld, Pluto was initially labeled a planet.
New Horizons launched in January 2006, just months before the International Astronomical Union demoted Pluto聽to "dwarf planet" status, in August 2006.
Before New Horizons, scientists knew a few things about Pluto. In 1978 an astronomer discovered Charon, Pluto鈥檚 largest moon. The four smaller moons in the system were discovered in the 2000s, with the last found in 2012.聽
They also knew that Pluto has an atmosphere and saw a surface pressure change in the atmosphere between 1988 and 2002, according to Olkin. They had also detected nitrogen and carbon monoxide on the surface from previous observations.聽
But New Horizons has brought Pluto into far sharper focus.
鈥淭he best image that we have of Pluto before New Horizons was just kind of a blur,鈥� Olkin says. That image was taken by the Hubble Space Telescope.聽
鈥淚t鈥檚 been very interesting to see the details on the surface and the complexity in this world鈥� right in our solar system, says Olkin. 鈥淚t鈥檚 like exploring your neighborhood.鈥�
