New Horizons sheds light on unusual cell-like formations marking Pluto's ice plains
A new image transmittedby NASA's New Horizons spacecraft has led mission scientists totheorize that sections of Pluto's heart-shaped plain behave much likea lava lamp – with blobs rising to the surface when warmed by thedwarf planet's internal heat, and sinking when they cool.
The image was capturedby the spacecraft's Long Range Reconnaissance Imager (LORRI) at adistance of roughly 10,000 miles (17,000 km) on July 14, 2015. Theshot covers an area 50 miles (80 km) wide and more than 400 miles(700 km) in length.
The unusual cell-likeappearance of the region surprised scientists across the world whenthey were first transmitted by the distant probe, and theories havebeen formulated ever since to address the unusual features. It isnow believed that the strange pits that permeate the landscape arethe result of a process known as sublimation.
On a larger scale, thecells observed from orbit, which measure 10-25 miles (16-40 km)across are believed to result from a mechanism by which the surfaceperiodically renews itself. The cell-like structure of the plainsowes its formation to a thermal convection process. Solidnitrogen would be warmed by Pluto's weak interior heat, becomingbuoyant and rising to the surface in a great blob from a reservoirwhich could, in places, be miles deep.
Parts of the raisededges of the cells are occasionally left behind, as thenitrogen-rich ice that makes up the bulk of each cell cools and fallsbeneath the surface. According to the team, such an event may havebeen responsible for creating the distinctive x-like artefactobserved in the image at the top of this page, which may once have been the meetingpoint of four separate cells.
According to missionscientists, the sporadic dark areas visible in the mosaic mayrepresent the presence of a contaminated block of water ice.
This process wouldeffectively allow a cycle of periodic rebirth of large sections ofSputnik Planum, and would explain the relative scarcity of impactcraters which would ordinarily mark the terrain.
A second compositeimage has been released by NASA, capturing a densely-cratered regionof Pluto informally designated Viking Terra. The observations weremade by New Horizons' LORRI instrument from a range of 31,000 miles(49,000 km), supplemented by data captured by the spacecraft'sRalph/Multispectral Visible Imaging Camera (MVIC).
The terrain captured inthe composite is roughly 160 miles (250 km) in width, displayingbright methane ice lining numerous crater rims. The ordinarily brightlandscape is blemished by dark red particles known as tholins.
Large quantities of thedarker particles appear to have flowed into a number of channels andcrater basins, leading mission scientists to theorize that thetholins are being manipulated by ice flows, or possibly even beingblown by Pluto's winds.
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