Tomorrow Pluto Flyby Will Send To Earth
TOMORROW, WHEN NEW Horizons makes its historic flyby of Pluto, it will be focusing in on just one face of the dwarf planet. In this latest photo captured by the space probe’s black-and-white LORRI camera, you can see that face—defined by a large, bright heart-shaped feature—beginning to rotate into view.
Only the top half of the heart is visible on the left side of this image, but come tomorrow, New Horizons will capture the valentine in full. (Viewers will have to wait up to a day and a half to actually see the image, since the probe will be too busy collecting data to send it back to Earth immediately.)
Rotating out of view, on the other hand, will be a number of other interesting geological details. The last good look New Horizons got of Pluto’s far side came in on Saturday. And this image is the best astronomers will get of the bullseye-shaped feature (to the right) that might be an impact crater. Without better images, the New Horizons team may never know for sure.
What have we learned so far?
The New Horizons team has already solved one of the biggest mysteries about Pluto: its size. This morning, NASA announced that Pluto is 2,370km (about 1,473 miles) in diameter, give or take 20m. That makes it ever so slightly bigger than Eris, a much darker and denser object that lives farther out in the Kuiper Belt. (Eris measures 2,336km in diameter.) Measurements of Pluto's size before today were estimates at best, their accuracy skewed by the dwarf planet's hazy atmosphere.
This morning also brought confirmation that Pluto has an icy polar cap, which is made of a mix of frozen methane and nitrogen gases. And while scientists had theorized that Pluto's thin atmosphere contained nitrogen, we've already learned that the gas is escaping Pluto's atmosphere much faster than expected.
What are we still unsure about?
A lot. The increasingly detailed views of the Pluto system have ramped up speculation about what geographic features might be found on its surface. A few of these were discussed in the morning briefing. Pluto may have a subsurface ocean, which could be evidenced by plumes escaping the planet — team scientists will be looking for those when New Horizons is behind Pluto looking back toward the Sun. While there are also a few large craters, Pluto's surface isn't as pockmarked as something like our Moon. That's a reflection of Pluto's more recent origins.
Many features are still to hard to resolve. For instance, the true nature of the large, black equatorial region is still unknown. There's also a mysteriously massive, white, heart-shaped region.
When will we see the Pluto system in high resolution?
NASA has been releasing incrementally better photos of Pluto and Charon for weeks now, but as New Horizons gets closer, the resolution of these photographs will increase exponentially. (The twitter bot NewHorizonsBot has been the best source for instant links to the newest uploads to the JUAPL server.) At around 11:15PM ET tonight, July 13th, the team will get a downlink from New Horizons that contains the best full-frame image from the black-and-white LORRI camera. (It will likely be released on the morning of the 14th, though.)
After this, New Horizons will "go dark" as it prepares for its flyby tomorrow morning. Because the spacecraft is zooming past instead of entering an orbit around Pluto, the spacecraft has to completely focus its instruments to take full advantage of its proximity. New Horizons will make that closest approach — about 12,500km (or 7,800 miles) — at 7:49AM ET.
All signs point to the spacecraft hitting its tiny 100km-by-150km (60 mile-by-90 mile) flyby window, and Stern said there's only a one in 10,000 chance that it will be impacted by debris. Still, New Horizons is traveling at about 31,000 miles per hour, so making contact with any piece of debris of significant size would spell immediate doom for the probe. NASA TV will hold a live broadcast for these activities from 7:30AM ET until 9:00AM ET.
Here's the stressful part: we won't know for sure that New Horizons successfully completed the flyby until much later in the evening. If it has, the team should receive a tiny amount of data from the spacecraft at about 8:53PM ET.
Wednesday morning, at 7AM ET, team scientists will downlink the best full-frame image of Charon. We should also get a glimpse of Hydra, one of Pluto's other moons. And later in the day we should get what we have all been waiting for — the first high-resolution mosaic of Pluto will be released some time around 3:25PM ET.
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