An Icy Brown Surface Hiding Gems
Observing details of Pluto surface was a dream for a long time. But the dream came true few years ago with a Pluto and Kuiper Belt reconnaissance flight: New Horizons Mission. The historical Pluto flyby in 2015 did not only change scientists perspective about Pluto, but also served extremely clear images of Pluto surface for everyone.
Here is the simulated but most realistic view of one section of Pluto’s hemispheres (See details about the far hemisphere on Far Side of Pluto article):
So what does above image reflect? What is Pluto made of?
World had to wait from 1930 till 2015 for such a detailed image and confident answers to above questions. By 1990‘s however, we had basic information about many Pluto facts and what she would be hiding from us. Out of several atmospheric investigations, scientists came up with proper information about Pluto atmosphere. As a result, we learned which molecules yielded the atmosphere.
What is more, estimating the environmental effects; same molecules were expected to be existing on Pluto surface. But without having a closer eye, it was not possible to be 100% sure about all. Besides, only the modeling data was available for a couple of decades.
Pluto Surface – Before and After New Horizons
Before New Horizons Mission, results of planetary models were indicating an icy surface, a geologically active body and a dark red color. As mentioned above, those were mostly a prediction and scientists needed more direct evidences. However, if you consider first paragraph of this sentence as a tiny abstract of structural Pluto information, actually they were right back than.
As New Horizons Spacecraft began its journey in 2006, the team on Earth started publishing images of different celestial objects on the way. But our fellow was still far away and no clear images were available for several years.
Than the spacecraft came along millions of kilometers in proximity as planned and became our eyes near Pluto surface for a short time. With a succcessful flyby, amount of our knowledge about Pluto surface features became enormous. When you have an images with huge resolution revealing details of 1.3 kilometers for a planet 4 billion kilometers away; and even focus on interesting features with dozens of meters/pixel resolution, you can easily call it a victory!
As a consequence of above, we owe most of our detailed and solid knowledge to New Horizons Mission. And we will mainly focus on scientific results of New Horizons flyby data and conclusions of researchers out of them.
It is not easy to comprehend, evaluate and interpret spectral data from a complete stranger face of a planet. Therefore it took some months for New Horizons Team to reveal basic secrets of planet Pluto after the most close-by images were captured. And from July 2015 till today, New Horizons team and other scientists kept on working, modeling and announcing new conclusions. We are still watching over her!
Pluto Surface Properties
Ok, what’s there on Pluto surface?
Pluto Surface – Structure, Composition and Temperature
In order to rid any curiousities from the beginning, let’s start with life on Pluto: None of the researchers encountered any Plutonians or signs of them on the surface. In other words, we can directly skip UFO conspiracies and focus on our primary subject with easy conscience. Yes, it is not a human face. Yes, there is not a fish on the surface!
Instead of alien life, on Pluto surface there are wide plain terrains, crater areas with various sizes, huge glaciers and rugged areas. Besides, there are intense mountanious zones where wide pits, scarps and eroded areas are visible. As a triggering effect of above; signs of glacialism, tectonism and cryovolcanism are easily concluded.
As different riverbed shapes observed, those features are interpreted as signs of cryovolcanic materials‘ erosive effects. Scientists believe similar features are available on Charon surface as well.
Looks like a proper world, a true planet! Right. Only if you neglect life and water.. OK, we did not see any creatures or plants over there. But where is the water on Pluto?
Well, it is cold out there.. Very cold. Pluto’s surface temperature is always below -200ºC. So do not expect waterfalls on the surface! But still there is enough amount of water ice on the surface which is close to 1% of Pluto surface. However, Pluto hides more water than you might think!
Rest of the surface is mostly made of nitrogen in ice form, together with other molecules like methane, carbon monoxide and ethane.
Pluto Surface – Activity and Regeneration
Infrared spectrometer measurements of Pluto surface features point out the existence of complex organic molecules called tholins on various terrains. Tholins are considered to be formed on most of the icy bodies in Kuiper Belt and generated via radiative effects of Sun. When it comes to tholins of Pluto, researchers believe they are either formed on surface via direct interaction of methane and nitrogen with radiation or with a similar process in the atmosphere, raining to the surface.
In addition to above, these formations are also simulated in labs and the way they are autonomously created in planetary environments is verifed. Even the experiments verified particularly the Plutonian Tholins!
Studies show that, although most of Pluto’s surface features render her age; Pluto surface is very active. Pluto regenerates the surface both by continuous condensation and sublimation processes; together with degradation, glaciation, cryovolcanism and tectonism. In addition to above, there are signs of regeneration via thermal convection especially in Sputnik Planitia area.
The water ice on surface of Pluto is mixed in dominant nitrogen and methane ices. And those materials are much more volatile than water ice. That’s why, they tend to rise to the top, hiding the water ice like a blanket.
Sputnik Planitia
Enveleoping a 1000 kilometers wide area, Sputnik Planitia is by far the biggest glacier and a unique feature in Solar System with broad nitrogen ice plains, deserving a seperate chapter.
One of Sputnik Planitia‘s several interesting features is that, the area is the most active and youngest region on Pluto surface: Less than 10 million years old.
The region is anticipated to be an ancient and huge valley of an impact, creating its own ambience in time. Throughout the years, volatile ices flowed from higher elevation fields around through Sputnik Planitia, thickened the crust and smoothened the surface. In addition to such gravitational effects, winds helped increasing the temperature and sweeped the materials all over. In contrast with above, distribution of craters on Pluto’s various surfaces and absence of them in Sputnik Planitia validates above inferences.
Sputnik Planitia’s effect on Pluto over years was so intense that scientists believe above processes might have even unbalanced her gravitational stability.
Beneath Pluto Surface
Let’s dive deeply in from Pluto surface and skip past kilometers of icy compounds where the crust ends.
Yeah, we believe Pluto might have an ocean beyond the surface. Even if it is not in liquid form, researchers are sure that big amount of water on Pluto is there beyond.
Beneath the ocean or an icy basin of water, there’s the dense core where the heavier elements incrassate. The core constitutes 65%-70% of Pluto in diameter.
What mostly makes researchers believe more in the idea of a buried ocean together with subalternate signs is the fact called tidal heating. As Pluto and Charon are mutually tidally locked to each other, such big gravitational influence on each other causes this extra heating. Is it enough to increase the temperature to melt the water ice? That’s the point where we might never be sure.
Pluto Surface – Further Understanding
Researchers believe above structural features are more or less valid for most of the Kuiper Belt Objects (KBO) in addition to Pluto. New Horizons Mission was the first and unique one to a KBO. And the scientists were happy that it was mostly affirmative about what they foreseen.
Above all, for better understanding Pluto, Pluto System or any other KBO; we still have a long way to go though.
Such understanding can come true with a future landing mission and good news is, scientists are already working on that!
UPDATED ON 5 OCTOBER 2019
References
- NASA
https://solarsystem.nasa.gov/planets/dwarf-planets/pluto/in-depth/ - 16 July 2018, “Pluto’s Underground Ocean” William Steigerwald,
https://nasaviz.gsfc.nasa.gov/13000 - 01-2015, “Geology Before Pluto: Pre-encounter Considerations“
Moore, Jeffrey M.; Howard, Alan D.; Schenk, Paul M.; McKinnon, William B.; Pappalardo, Robert T.; Ewing, Ryan C.; Bierhaus, Edward B.; Bray, Veronica J.; Spencer, John R.; Binzel, Richard P.; Buratti, Bonnie; Grundy, William M.; Olkin, Catherine B.; Reitsema, Harold J.; Reuter, Dennis C.; Stern, S. Alan; Weaver, Harold; Young, Leslie A.; Beyer, Ross A.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140013378.pdf - 11-2015, “Geology of Pluto and Charon Overview“
Moore, Jeffrey M.; Stern, S. A.; Weaver, H. A.; Young, Leslie A.; Ennico, Kimberly; Olkin, Cathy B
https://arxiv.org/ftp/arxiv/papers/1604/1604.05702.pdf - 11-2015, ” Processes Modifying Cratered Terrains on Pluto“
Moore J.M.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150021036.pdf - 04-2016, ” The Geology of Pluto and Charon Through the Eyes of New Horizons“
Jeffrey M. Moore, William B. McKinnon, John R. Spencer, Alan D. Howard, Paul M. Schenk, Ross A. Beyer, Francis Nimmo, Kelsi N. Singer, Orkan M. Umurhan, Oliver L. White, S. Alan Stern, Kimberly Ennico, Cathy B. Olkin, Harold A. Weaver, Leslie A. Young, Richard P. Binzel, Marc W. Buie, Bonnie J. Buratti, Andrew F. Cheng, Dale P. Cruikshank, Will M. Grundy, Ivan R. Linscott, Harold J. Reitsema, Dennis C. Reuter, Mark R. Showalter, Veronica J. Bray, Carrie L. Chavez, Carly J. A. Howett, Tod R. Lauer, Carey M. Lisse, Alex Harrison Parker, S. B. Porter, Simon J. Robbins, Kirby Runyon, Ted Stryk, Henry B. Throop, Constantine C. C. Tsang, Anne J. Verbiscer, Amanda M. Zangari, Andrew L. Chaikin, Don E. Wilhelms
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170000011.pdf - 4-2016, “The Geology of Pluto and Charon as Revealed by New Horizons“
Jeffrey M. Moore, John R. Spencer, William B. McKinnon, S. Alan Stern, Leslie A. Young, Harold A. Weaver, Cathy B. Olkin, Kim Ennico, New Horizons GGI Team
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160005165.pdf - 12-2005, “Tholins As Coloring Agents On Pluto and Other Icy Solar System Bodies“
Dale P. Cruikshank, Hiroshi Imanaka, Cristina M. Dalle Ore
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160009761.pdf - 7-2016, “Pluto and Charon Seen with the New Horizons Spacecraft“
Cruikshank D. P, Stern S.A, Weaver H. A, Young L.A, Ennico K, Olkin C.B.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160009762.pdf - 6-2017, “The Chemistry of Pluto and its Satellites“
Dale P. Cruikshank
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170005654.pdf - 03-2019, “Fifty Years of Exploring Pluto: From Telescopes to the New Horizons Mission”
D. P. Cruikshank, S. A. Stern, H. A. Weaver, C. B. Olkin, L. A. Young, K. Ennico, F. Bagenal, New Horizons Science Team
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190002167.pdf
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