What we will and will not see during the Pluto fly-by


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Pluto's two hemispheres

The images above, released today by the New Horizons’ science team, provide the best global view so far of Pluto’s two hemispheres. I have cropped and rearranged the original to focus on Pluto.

The images illustrate some basic new knowledge about the planet. For one, scientists have now identified the planet’s poles, based upon its rotation. While scientists had had a very rough vague idea of Pluto’s rotation and inclination beforehand, they have now pinned it down pretty precisely.

The images also show the planet’s most striking and unique features, though not with enough resolution to tell us what they are.

New color images from NASA’s New Horizons spacecraft show two very different faces of the mysterious dwarf planet, one with a series of intriguing spots along the equator that are evenly spaced. Each of the spots is about 300 miles in diameter, with a surface area that’s roughly the size of the state of Missouri.

Scientists have yet to see anything quite like the dark spots; their presence has piqued the interest of the New Horizons science team, due to the remarkable consistency in their spacing and size. While the origin of the spots is a mystery for now, the answer may be revealed as the spacecraft continues its approach to the mysterious dwarf planet. “It’s a real puzzle—we don’t know what the spots are, and we can’t wait to find out,” said New Horizons principal investigator Alan Stern of the Southwest Research Institute, Boulder. “Also puzzling is the longstanding and dramatic difference in the colors and appearance of Pluto compared to its darker and grayer moon Charon.”

This image release also shows us what we will and will not see during the fly-by. The image on the left is the “encounter hemisphere.” This is the hemisphere that will be in view during New Horizons’ July 14 fly-by. We shall get very nice high resolutions of much of this hemisphere.

The other hemisphere, however, will not be facing us during the fly-by. Unless that can get some high resolution images before it rotates out of view, the row of large dark spots at the equator will remain a mystery.

The images also suggest that, because of Pluto’s tilt, much of the southern hemisphere is not going to be seen at all. It will remain an additional mystery for the many decades that are going to pass before another spacecraft finally returns to this distant place.

6 comments

  • Nick P

    Bob

    “It will remain an additional mystery for the many decades that are going to pass before another spacecraft finally returns to this distant place.”

    And sadly, that will be beyond the lifetimes of many here. Still, I grateful for what we will have. It’s more than any human has ever seen before, at least as far as we know…

  • Its no doubt New Horizons will get interesting data as it leaves the solar system just as Voyager 1 and 2 did. But as we get closer to passing Pluto it feels like we missed a great chance to spend some time in orbit of a very interesting planetary system rather than a few seconds there.

    That data will be interesting and hopefully New Horizons will find other objects to pass by but considering how complicated it has been just to make sure we don’t miss Pluto which we know a fair bit about compared to other Kelper belt objects. The chances of a another encounter seems kinda low.

  • DougSpace

    I’m wondering how much of the non-encounter hemisphere we will see due to Pluto’s rotation before and after the flyby as well as the flyby seeing a little bit of one side and the other.

  • DougSpace

    Maybe a small craft could have been released previously so that it flew past the other side at the same time and then beamed the image data back to the mothership.

  • Edward

    DougSpace,

    Since the planet is well lit as New Horizons approaches, after the closest encounter the craft will likely face the dark side, so I suspect that there will be few good photographs after the encounter — unlike the approach.

    This is probably all for the best, because having a well lit planet on approach allows the team to analyze and pre-plan what they most want to investigate during the encounter.

    The small daughter-craft could have been a good idea, although the opposite side may be the dark side, when New Horizons passes by. The mission planners had to seriously consider their weight limitations, so a daughter-craft was probably never a possibility.

    If they had had more weight available to them (a lot more), they could have loaded up more fuel in order to enter orbit and then they would have been able to examine the planet at their leisure. It would have been like the difference between the Giotto probe’s fly-by encounter with Halley’s Comet and Rosetta’s orbital encounter with Comet 67P.

    Not all is lost, though. Pluto’s 6-day rotation should give us another couple of looks at the side in question.

  • wodun

    “But as we get closer to passing Pluto it feels like we missed a great chance to spend some time in orbit of a very interesting planetary system rather than a few seconds there.”

    The problem is that it is moving too fast. As Edward alludes to below, more fuel would have been needed to slow the craft down enough to maintain an orbit.

    I have no idea about the orbital dynamics involved or how much fuel would be needed to slow down.

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