Water ice concentration on Pluto surface

Water On Pluto – Dominator Of The Underground

Looking for Water? Plenty of It Exists on Pluto!

Water on Pluto welling up!

Water implies life. The living creatures we know either need water or postpone their need in a stand-by mode.

Although life in other worlds needs several different conditions to be settled, water is used to be the most popular one. Luckily discovery of thousands of exoplanets recently broke this chain and now the global mainstream is mentioning about “life zones” (Habitable Zone) instead of existence of water only.

Despite above, mainstream had a point about praising water before the exoplanets became popular: When it comes to planets and moons within Solar System, water is one of the unique sources we can search for. The reason is, we understood that they don’t currently meet rest of the requirements in general!

Luckily we have outer Solar System. Discoveries about existence of big amount of water on moons of Gas giants and Kuiper Belt Objects bring a broad perspective about water and its consequences.

Kuiper Belt
A Kuiper Belt illustration. Source: NASA

At the end of the day, scientists are not only interested in the seeds of life: Water on other planets have quite many features to count. Especially for the ones dominated by water.

Hence, this article is mainly interested in not only its effects about extraterrestrial life, but also the existence of water on Pluto and various formative effects of its ice form on rocky objects.

Water On Pluto – Where Does It Come From?

How Is Water Produced In Universe

H2O: Combination of elements hydrogen and oxygen. And we do know where both comes from: Stars.

Primary materials of the universe and all stars are hydrogen and helium, which is a product of late Big Bang times. And as those stars grow up, they start to produce new materials via nuclear reactions. What is more, one of the next phases of bigger stars includes the production of oxygen.

Luckily the most common elements in the universe are hydrogen, helium and oxygen respectively. This creates a big opportunity for water, as hydrogen and oxygen are truely inclined to bond.

Water. Source: Wikipedia

How Did The Loafing Water Arrive Pluto Lands?

OK, we know water is floating in the space. But how did the water arrive to Pluto in the first place?

Well, it was already there! For answering that, we need to go back to formation of Solar System and Kuiper Belt.

Every single thing in the universe is a consequence of older stars. So is our Sun! This means, the clouds and the dust, which was the initial state of Solar System, was already including the water! The rest is all about chaotic birth of Solar System and distribution of materials all around.

Water ice is literally everywhere. Hence Pluto got its share too!

Survival of Water on Pluto

“Hello, Celestial Object. You might have water, but you need to know how to keep it!”, a wise man says.

Enceladuus
Saturn’s moon Enceladus listened to that wise man. Source: NASA

As explained above, there is enough water everywhere.. The point is not losing it. Look at solar system planets. As of today, all of them have water in different forms except Venus.

Actually a planet should be quite unlucky to lose all the water onboard. In Venus’ case, the Sun did not behave well to it.. In the past, poor Venus did have water.

Venus is the hottest planet in Solar System. And scientists believe the extreme temperatures caused the water completely evaporate. What is more, proximity between Venus and the Sun let Solar Winds sweep it off completely.

When it comes to water on Pluto: Nema problema! Pluto’s surface and atmospheric temperature is always below -200ºC. That preserves existence of water in ice form on the surface.

Pluto
Here comes Pluo. Source: NASA

Researchers believe that beyond the surface Pluto has a hidden ocean. But since it’s covered with a thick and icy crust, Pluto will not let it go away! And such formation will not allow solar winds to touch precious water lands!

As a conclusion, above also explains why all rocky objects in Kuiper Belt region and moons of Gas giants have confident amount of water reserves.

Water on Pluto – How Was It Detected?

There are several ways to do that.

One indirect proof is the density. Pluto’s density is 1.88g/cm³ and 70% of Pluto is made of a rocky core. Researchers easily conclude that rest of the surface and crustal material should be dominated by water ice on Pluto.

Observations via stellar occultation methods from the end of 1980’s were aiming to examine Pluto atmosphere. Those studies were also supportive about detecting signs of water on Pluto.

Pluto atmosphere
Pluto atmosphere with a bright haze layer. Source: NASA

But the first direct verification was performed via Hubble Space Telescope spectrometers in 1994, which concluded the existence of water ice on Pluto surface.

The next source was the New Horizons Mission: Beginning with the closest Pluto encounter in July 2015, scientists had a clear view of all above and they verified once more: There is big amount of water on Pluto!

Water Concentration on Pluto

As mentioned above, calculated total amount of water on Pluto in ice form is about 30% of the planet, where the rest 70% is made of the core with silicates.

Pluto inner layers
Basic view of Pluto’s inner layers. Liquid water can still be alive between water ice and rock. Source: NASA / Pat Rawlings

Despite of this water intensity, Pluto is obliged to hide most of the water ice. When New Horizons Team finished mapping the Pluto surface, calculated amount of water ice was only less than 1%. After they found signs of such coverture made mostly of nitrogen, they were convinced about beyond the surface: All was hiding there!

We’ve stated that “30% of water is in ice form“, however that may not be completely true: Scientists believe there is an underground ocean hidden behind Pluto’s crust and that would slightly change the game!

Water on Pluto – Details About New Horizons Mission Findings

More common water ice planes than thought!

Concentration of water on Pluto surface
Two different water ice concentration maps of Pluto. Source: NASA

NASA released above image on 28 January 2016 on the New Horizons Mission web page, half a year later than its closest approach. The image shows basic results of one of the most important Pluto facts: Calculated water ice concentrations derived with two different techniques.

Why are there two different images regarding water on Pluto? And why does the amount of water ice on Pluto surface varies dramatically? We’ll go further in details.

One thing to note down before doing that: Those interpretations depend only on one hemisphere. And there are no detailed surface information for the other part yet. The reason behind this is, New Horizons captured those images while it was flying by Pluto System and this half of Pluto was in day light.

Actually there are additional images from the non-encountered hemisphere of Pluto during close approaches of New Horizons as well. However those images were obtained either with lower light reflection or aimed to observe Pluto atmosphere from “night zone” which makes major surface analysis impossible.

Pluto atmosphere, zoomed in
An example Pluto image from the dark side, revealing details of the atmosphere. Source: NASA

Pluto’s Water Ice Concentration Maps

Let’s come back to the water ice concentration maps.

Both images were taken with Ralph and LEISA (Linear Ethalon Imaging Spectral Array) instruments equipped onboard New Horizons Spacecraft. In addition, the images are produced on infrared wavelengths and captured 108.000 kilometers away from surface.

While Ralph is responsible for both visible and infrared imaging, LEISA is the instrument specialized for surface material duties as it is capable of capturing specific infrared wavelength from its every single pixel.

This is how you can detect water ice on a solar system planet surface: You need to analyze the sunlight reflected from planet surface and detect the light spectrum of water ice.

Since the surface includes methane ice as well, this time it was little bit hard to distinguish. Because the spectral wavelengths of methane and water ice are very close. That’s why the image on the left did not reflect the best estimation.

Colors mentioning height
Not an image for mapping water on Pluto. Just an elevation map! Source: NASA

Than the researchers decided to apply another algorithm for better interpretation of water ice on Pluto surface. They focused on every icy part on planet surface; which could be the ice layers of nitrogen, methane or carbon monoxide as well. While total amount of water ice on Pluto is small comparing to other materials on surface, this is a more effective method and revealed better estimations considering the hidden water ice beneath other materials.

How much water ice exists on and beneath Pluto surface? We are not quite sure yet. Existence of methane is still deceiving and the map on the right side lacks perfection too. However researchers are still working hard to expose more secrets.

Formation of Water on Pluto and Its Consequences

As a conclusion of above, water ice is clearly the basic material of Pluto outside its core. Pluto is a world made of water ice!

Water Ice As a Building Stone

Water is the unique construction material sited in the mountains, valleys, scarps and everything by help of other materials and tectonism. Everything else above and combined with it are the “rest of Pluto materials“. They just seem to be decoratively sprayed on top of a thick water ice crust..

Alcyonia Lacus
Alcyonia Lacus: A frozen lake on Pluto surface. Source: NASA

Erosion of Water Ice on Pluto Surface

Appearance can be deceiving.. Those are not purely decorative.

The dominant surface material nitrogen together with carbon monoxide are denser than water ice at Pluto’s surface temperatures. Hence they are anticipated to be the source of erosion on most areas: They float over the surface and produce different surface features over long periods via winds and sublimation.

As you go down to deeper levels of water ice, it will get more compact and dense. Hence the weakest water ice can be considered as the ones close to the surface. However those can help the erosion too: Water ice erodes and scraps itself.

Cryovolcanism on Virgil Fossae: Water Comes In Sight

Scientists has another interesting inference.

Virgil Fossae
Water ice distribution on Virgil Fossae area. Source: NASA

Check out the dark blue and water-dense area on the global concentration map: This region is located on west side of Sputnik Planitia and called Virgil Fossae. What caused water ice to come out? Researchers came out with a seperate story about that: This could be a sign of cryovolcanism on Pluto.

A cryovolcano spits volatile materials like methane and water ices above surface of celestial objects. Researchers believe that the signs of sweeped material and eroded surface is the first, and the amount of water ice and methane exposure through the surface is the second strong suggestions of such incidents from past. They believe those facts can not simply be explained as “coincidence“.

Can Water on Pluto Host Life?

Let’s list what we have here:

  • Pluto has big amount of water, mostly in ice form.
  • Possibly has an underground ocean.
  • Has complex organic molecules called tholins.
Pluto ocean
Pac-Pluto, opening her mouth full of water. Credit: Pam Engebretson, Soure here

Above is a part oflife kit“. But, are above sufficient for triggering formation of life? We don’t have an answer yet. But the answer is a big NO by means of complex life.

On the other hand, most of the theories about primitive life claims the foundation was laid in deep oceans. However it’s not that simple to conclude everything with an ocean. For instance, we believe there’s not enough oxygen over there, and this can easily break the deal.

Above all, we believe the concept of “life on other planets” will remain as a speculation until scientists literally find a living creature and confirm that.

References

  • NASA:
    01-2016, “Pluto’s Widespread Water Ice
    https://www.nasa.gov/image-feature/pluto-s-widespread-water-ice
    04-2015, “The Solar System and Beyond is Awash in Waterhttps://www.nasa.gov/jpl/the-solar-system-and-beyond-is-awash-in-water
    12-2015, “Pluto Through a Stained Glass Window: A Movie From the Edge of Our Solar System”
    Bill Keeter
    Link: ( https://blogs.nasa.gov/pluto/2015 )
  • 06-2017, “The Chemistry of Pluto and its Satellites”
    Cruikshank, Dale P.
    Link: ( https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170005654.pdf )
  • 03-2016, “Surface Compositions Across Pluto and Charon”
    W. M. Grundy, R. P. Binzel, B. J. Buratti, J. C. Cook, D. P. Cruikshank, C. M. Dalle Ore, A. M. Earle, K. Ennico, C. J. A. Howett, A. W. Lunsford, C. B. Olkin, A. H. Parker, S. Philippe, S. Protopapa, E. Quirico, D. C. Reuter, B. Schmitt, K. N. Singer, A. J. Verbiscer, R. A. Beyer, M. W. Buie, A. F. Cheng, D. E. Jennings, I. R. Linscott, J. Wm. Parker, P. M. Schenk, J. R. Spencer, J. A. Stansberry, S. A. Stern, H. B. Throop, C. C. C. Tsang, H. A. Weaver, G. E. Weigle II, L. A. Young, New Horizons Science Team
    Link: ( https://arxiv.org/ftp/arxiv/papers/1604/1604.05368.pdf )
  • 00-1990, “Triton, Pluto and Charon
    Cruikshank, Dale P.
    Link: ( https://www.sciencedirect.com/science/article/pii/0273117790901059 )
  • 11-1980, “Mass-radius Relationships and Constraints on the Composition of Pluto
    Mark J. Lupo, John S. Lewis
    Link: ( https://www.sciencedirect.com/science/article/abs/pii/0019103580902389 )
  • 4-2012, “Water ice in the Kuiper Belt
    M.E. Brown, E.L. Schaller, W.C. Fraser
    Link: ( https://arxiv.org/abs/1204.3638 )
  • 4-2019, “Recent cryovolcanism in Virgil Fossae on Pluto”
    Dale P. Cruikshank, Orkan M. Umurhan, Ross A. Beyer, Bernard Schmitt, James T. Keane, Kirby D. Runyon, Dimitra Atri, Oliver L. White, Isamu Matsuyama, Jeffrey M. Moore, William B. McKinnon, Scott A. Sandford, Kelsi N. Singer, William M. Grundy et al.
    Link: (https://www.sciencedirect.com/science/article/abs/pii/S0019103518307346)
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