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Last Look at Pluto’s ‘Far Side’

The side of Pluto that always faces its large moon Charon is the side that New Horizons won’t see when it makes its close flyby on July 14. That makes the image below what principal investigator Alan Stern is calling “the last, best look that anyone will have of Pluto’s far side for decades to come.”


Image: New Horizons’ last look at Pluto’s Charon-facing hemisphere reveals intriguing geologic details that are of keen interest to mission scientists. This image, taken early the morning of July 11, 2015, shows newly-resolved linear features above the equatorial region that intersect, suggestive of polygonal shapes. This image was captured when the spacecraft was 2.5 million miles (4 million kilometers) from Pluto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

Four dark spots seem to be connected to the dark belt in Pluto’s equatorial region, their fairly regular spacing a source of considerable curiosity. The large areas are estimated to be roughly 480 kilometers across, with irregular boundaries between light and dark terrain. Jeff Moore (NASA Ames) gives a glimpse of what’s ahead:

“When we combine images like this of the far side with composition and color data the spacecraft has already acquired but not yet sent to Earth, we expect to be able to read the history of this face of Pluto.”

And of course, as this JHU/APL news release reminds us, we’ll soon be seeing the encounter hemisphere from as close as 12,500 kilometers.


Comments on this entry are closed.

  • J. Jason Wentworth July 11, 2015, 22:35

    An ejectable camera (like the one or two the IKAROS solar sailcraft ejected to photograph itself) would have been very useful for getting complete, close-up coverage of Pluto’s Charon-facing hemisphere (and perhaps also of Charon’s Pluto-facing hemisphere), but the cost–like that of the proposed Russian-supplied “drop zond” for New Horizons–would likely have scuttled the mission before it could fly. But:

    Filling this gap would be a perfect mission for beam-pushed sail probes, of either the solitary or “swarm” variety. The Uranus and Neptune systems, through which Voyager 2 took fascinating but hardly comprehensive “lightning tours,” would also be worth visiting again by means of such probes. While flybys aren’t as desirable as orbital surveys, numerous flybys could be almost as useful, especially if cheap, mass-produced sail probes (propelled by an “engine” that is reusable and stays close to home) were used instead of much smaller numbers of larger, more expensive spacecraft.

  • LocalFluff July 11, 2015, 23:43

    That’s disappointing! But I suppose it is the far side as a whole, and that much of it will have higher resolution. This isn’t much better than Luna 3 in 1959.

  • DCM July 12, 2015, 4:20

    After going all that way you’d think they’d have designed it to remain in orbit and thoroughly explore Pluto from above.

  • gnappi July 12, 2015, 12:31

    Pluto has lakes!!! Lakes of liquid nitrogen. Due to the orbital inclination, currently the equatorial region receives less light than the North pole of the dwarf planet, so the nitrogen can remain liquid at low latitudes, whereas the illuminated pole it evaporates and “migrates” to the non-illuminated side (South pole) and condenses as ice (nitrogen ice).

  • Malcolm Davis July 13, 2015, 0:28

    From what I’ve read on social media, the resolution is meant to get better as information currently stored on New Horizons is sent back to Earth, so hopefully this is not the best view of Pluto we get for decades. So far, the resolution of the imagery is not the best. If this is as good as it gets, then its a serious let down in my view. So I’m hoping the discussion on social media is correct, and we are yet to see better resolution imagery.

    But I also think that there is a strong case to make that exploring the deep outer Solar System (beyond Saturn) really does demand some innovative new thinking on propulsion and spacecraft design. Its taken fifteen years for New Horizon to get to Pluto, and its flyby will be over very quickly, with no possibility of decelerating into orbit. Certainly there are other Kuiper belt objects to explore, but its shame that New Horizons could not have dropped off some mini-orbiters or landers along the way. But the next probe to Pluto needs to get there much faster, and should have the ability to go into orbit to do an intensive survey of what is clearly an interesting planetary system. That demands something better than chemical rockets and gravity assist – spacecraft nuclear power and propulsion is essential in my view.

  • Kappy July 13, 2015, 0:40

    @DCM – Surely mission planners would have loved to orbit Pluto rather than a fast flyby, however Pluto is very far from Earth. In order to enter orbit a Pluto, NH would have to either be traveling much more slowly, which would require a much longer travel time (I think I read 40 years rather than the 9.5 NH took), or would have had to carry significantly more fuel (which was technically unfeasible with the budget and launch equipment we have today). Having NH as a fast flyby mission was the only reasonable way to get the mission approved and to arrive before the 2030s/2040s.

    @gnappi – Despite what they look like, it’s highly unlikely that Pluto has active liquid lakes. Although some areas of the dwarf planet might maintain temperatures where certain elements could remain liquid, the lack of a sufficient atmosphere means that liquids would sublimate away and would thus not be stable for long periods of time. One theory/possibility for stable liquid bodies on the surface though is that they are neon lakes, which would be very interesting indeed.

  • Harry R Ray July 13, 2015, 9:22

    gnappi/Kappy: You may BOTH be right! Here’s why. Triton has SIMILAR formations to the four Plutonian “Dark Spots”, albeit MUCH SMALLER! I have ALWAYS theorized that, on Triton, these features are liquid nitrogen lakes UNDER a TRANSPARENT VENEER of frozen nitrogen ICE that keeps the lakes from evaporating! My ONLY critique of applying it to MUCH LARGER Plutonian MARE (they ALL seem to be TOO BIG for lakes, and they look REMARKABLY LIKE the Mare on TITAN) is that, on Triton, you clearly see OPAQUE NITROGEN ICE completely surrounging the lake “candidates”, whereas this appears NOT to be the case on Pluto.