New Horizons at Io Options

[volcanopele]

Since the New Horizons Jupiter Encounter thread is already getting pretty long, I decided to create a thread dedicated to New Horizons' observations of the most interesting object in the solar system: Io. Info on upcoming observations comes from the jupiter_timeline_static.xls document john_s posted, and the preview images are from Celestia (note that each image is scaled so that the pixel scale is ~correct, and represents a smaller FOV than LORRI)

Today, February 24, New Horizons conducts three observations of Io with the LORRI camera as well some observations of Io's atmosphere with ALICE. These observations have the lowest phase angle for Io of the entire encounter. Phase angle continues to increase as NH approaches Jupiter and Io.


The first observation, ISunMon1, shows Io's sub-Jovian hemisphere (Clat=5.5 S, Clon=340.2 W) from a distance of 7,856,307 km. The resolution with LORRI would be 38.8 km/pixel. Pele is on the limb at lower right and Masubi is on the limb at lower left. Ra Patera is near center.


The second observation, ISunMon2, also shows Io's sub-Jovian hemisphere (Clat=5.5 S, Clon=15.1 W) from a distance of 7,575,510 km. The resolution with LORRI would be 37.5 km/pixel. The Tvashtar plume might be poking above the limb at upper left.


The third observation, ISunMon3, shows Io's leading hemisphere (Clat=6.0 S, Clon=84.7 W) from a distance of 6,627,459 km. The resolution with LORRI would be 32.8 km/pixel. The Zamama plume might be visible just above center on the left limb.

It only gets better from here. Not sure how NH downlink works, but there is a DSN window right after the last Io observation, hopefully at least one frame from each observation will be returned. Maybe they can do the Huffman window right around where Io is... Tomorrow contains four more observations of Io, highlighting Pele and an eclipse.

[volcanopele]

COOL! Looks like their are two plume sources at Masubi.

[ugordan]

Could we be seeing another plume at around 5:30 on the limb? There's some suspicious fuzzyness there.

[volcanopele]

Could we be seeing another plume at around 5:30 on the limb? There's some suspicious fuzzyness there.

I noticed that too. Can't be sure just from this image, hopefully we can say for sure when the rest of the images come down.

Some thing to look for. Good Eyes!

[ugordan]

Here all the visible plumes as well as my candidates for additional discrete plumes so far:

The Tvashtar eruption seems like a double plume.

[volcanopele]

Good eyes.

With out a lat-lon grid this is difficult to assess, but I'll give it a stab. Let's assume for a moment that those bumps at 5 o'clock and 5:30 are real features (they might be, they might not be, difficult to say). The bump at 5:30 might be a plume associated with the volcano Aramazd Patera. The bump at 5 o'clock I think is the mountain Euboea Montes.

[ugordan]

The 5:30 feature definitely makes for a more convincing case than the 5 o'clock one. You're probably right on it being a mountain. The Tvashtar plume either got a weird twist or there's also something else erupting there.

[Bjorn Jonsson]

WOW!! This may be the most dramatic image I have ever seen of Io's plumes. And not unexpectedly, LORRI is very sensitive - does anyone know the strength of Jupitershine on Io's nightside as compared to sunlight at Pluto?

And here is a rendering showing the viewing geometry:

[Stu]

Hands up confession time... I've never really been that excited by Io (ducks to avoid slapping hand of volocanopele! ) but wow, that image is a stunner... the detail in that plume is just incredible.

Imagine what that would have been like in colour...

[ugordan]

After closest approach, Io's quickly reduced to a waning crescent, allowing for longer exposures. While the resolution will rapidly diminish, we should be able to see numerous plumes crop up in scattered light and jupitershine. And likely with some (low resolution) color, too!

What a great week!

[TritonAntares]

...

...
Amazing, simply amazing.

Really picturesque. Impressive what NH cameras can achieve with the dark Io-hemisphere in jupitershine.
Makes us hope for Pluto and Charon - even if it's much darker out there!

Btw., there are some mensae visible at the terminator, here a nice close up of such mountains imaged by Galileo:


Bye.

[Stu]

[john_s]

Imagine what that would have been like in colour...

Patience- there will be colo(u)r! We got a lower-resolution color scan with MVIC at the same time, but it won't be sent down for a month or more. We'll do some cool colorization then, I'm sure.

John.

[dilo]

Great colorization, Stu!!!
Waiting for the full picture...
(sad to think we will not see such kind of images for a while, even if with the most advanced AO telescopes the particular geometry/lighting which make possible to see such volcanoes and mountains aren't possible from Earth!)

[Bjorn Jonsson]

Here is a properly shaded version with exaggerated Jupitershine showing at higher resolution what's visible in the NH image. As discussed when the first Io images appeared some changes are visible.

In addition to a texture map I used a crude elevation map where I 'manually' painted in all of Io's major mountains using a table from a paper published in Icarus (or possibly JGR - I'm too lazy to check) several years ago as a guide. In addition to the table I also used various images as a guide. This now seems to have been more successful than I thought although various 'errors' can be spotted. Various mountains and mesas are obvious near the terminator.

[Stu]