you're reading...


Pluto perhaps not so icy after all

Hammond, Noah P., Amy C. Barr, and Edgar M. Parmentier. “Recent Tectonic Activity on Pluto Driven by Phase Changes in the Ice Shell.” Geophysical Research Letters (2016). DOI: 10.1002/2016GL069220


Figure 1 – Artist rendering of New Horizon passing Pluto. Courtesy of NASA/JHU APL/SwRI Steve Gribben

Pluto, the celestial object formerly known as a planet, got a close look from a passing NASA spacecraft last summer. New Horizons was launched in January of 2006 to study the cloud of small objects at the edge of the solar system called the Kuiper belt (Fig 1). Nine years later, it passed by Pluto, in the process capturing the most detailed observations of the plane…er…astronomical body to date.

A few months ago, scientists released a paper describing these new high-resolution images that New Horizon captured of Pluto. Their analysis suggested that many of the surface features are relatively young and, therefore, not formed by tectonic activity. The discussion left open the tantalizing possibility that the surface was shaped by glaciers and oceans.

Enter Noah Hammond, a graduate student at Brown University. Along with his advisors, he set out to try and explain how these surface features might have formed. Their analysis revealed something surprising: it’s possible there a liquid ocean on current day Pluto. Water. Approximately 5 billion kilometers from the sun. On an object whose surface temperature hovers at about 40 Kelvin (or -233°C/ -384°F).

Arriving at this conclusion took a lot of work and computer wrangling. Hammond started by simplifying Pluto’s geometry and breaking it into lots of little boxes. What is happening in each box is described by a mathematical relationship between many parameters — things like temperature, time, and density. Hammond was able to poke and prod his theoretical Pluto by varying these parameters and watching what how it’s thermal properties changed in time.

The team assumed that the dwarf planet has a solid core with a separate ice layer on top. While there is ample evidence suggesting this is the case, scientists are unsure of the exact make-up of the core. The composition of Pluto’s center is an important component of Hammond’s model since different materials transfer heat differently. To account for that uncertainty, Hammond varied the core’s thermal conductivity, a number indicating how well a material conducts heat.

As the model evolved under each set of conditions, Hammond watched for phase changes in the water. When ice melts or water freezes, the volume of the material changes. Likewise, at certain temperatures and pressures, such as those on Pluto, ice can become a denser material called ice II. At large scales, these shifts in phase would alter the volume of the whole planet: as water expands into ice, the volume will go up. As ice condenses into ice II, the object will shrink.


Figure 2 – Graphs illustrating the Plutonian ocean evolution over time. The x-axis is in millions of years. The top graphs have a y-axis of depth from the core to the surface. The bottom ones show stress in Pascals. (a) are the end result of a warm scenario. At the end of model run, there is liquid water and the net force is extensional. (b) shows a cold scenario. At the models end, there is no water, but a lot of ice II. The force is net compressional. Adapted from Hammond et al., 2016.

Hammond’s model settled into either a “warm” or “cold” final state depending on the thermal properties of the core. In warm scenarios, a 50 km thick ocean forms beneath 250 km of ice and persists to the present day (Fig 2a). Leading up to the cold outcome, the ocean completely froze before the model time ended time. But the increased pressure from more ice resulted in the formation of ice II (Fig. 2b).


Figure 3 – Image of Pluto’s surface from New Horizon. The areas marked (b) show flow lines associated with glacial features. The inset at bottom right shows a close up. Adapted from Moore et al., 2016.

These very different end states have similar planetary effects: dramatic shifts in Pluto’s volume. The formation of ice II would cause global contraction. The formation of ice from water would result in global expansion. Hammond argues the liquid water case is more likely. He points to the surface features observed by New Horizon, which were likely cause by extensional, rather than compressive, forces.

Is there actually water on Pluto, buried beneath miles of ice? We may never know for sure, but Hammond suggests the New Horizon data can be used to verify his findings. More detailed analysis of the images could verify that the observed geographic features are from expansion forces and verify the timing of the events. Maybe after that NASA will support an expedition to Pluto. Who knows what it might find. I am banking on space whales.


No comments yet.

Post a Comment


  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 6 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 9 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 9 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 9 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 10 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 11 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 11 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 12 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 12 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 1 year ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com