Nasa Picks "juno" As Next New Frontiers Mission Options

[Guest_BruceMoomaw_*]

http://www.nasa.gov/home/hqnews/2005/jun/H...rontiers_2.html

Yeah, I know it ain't Saturn, but we don't seem to have any proper slot for Jovian news -- including yesterday's totally unexpected announcement that Amalthea's density is so low as to suggest that it's a highly porous ice object; maybe a captured Kuiper Belt Object reduced to rubble by infalling meteoroids. As Jason Perry says, this might explain those previously mysterious light-colored patches on Amalthea -- they may be its underlying ice, exposed by impacts that punched through the layer of sulfur spray-painted onto it by Io.

Scott Bolton has been pretty talkative to me already about the design of Juno. It certainly won't be as good in the PR department as Galileo or Cassini, but it DOES carry a camera -- as much for PR as for Jovian cloud science, according to Bolton. And since the latitude of periapsis of its highly elliptical orbit will change radically during the primary mission, I wonder if they might be able to set up at least one close photographic flyby of Io and/or Amalthea? (I believe, by the way, that this selection is a bit ahead of schedule -- and it certainly indicates that NASA's science program under Griffin won't be a complete slave to Bush's Moon-Mars initiative.)

[Guest_BruceMoomaw_*]

While the new Solar System Roadmap (or, rather its first draft -- it's about to undergo some minor revisions) has just been yanked back off the Web (along with all the other new Roadmaps) by NASA within a few days of being put there, I copied them all first. Two things about the Europa Orbiter:

(1) It will actually be the first of a new cost class of Solar System missions -- which were called "Intermediate" missions at the first meeting of the Roadmap committee when I attended it, but are now referred to as "Small Flagship"
missions. These are missions in the $700 million to $1.5 billion class. One thing that killed Europa Orbiter last time was the fact there was a $1 billion cost cap on it, and JPL concluded that it simply could not be done -- even in stripped-down form -- for less than about $1.2 billion. (The next two Small Flagship missions -- spaced at intervals of about 5 years -- will be to Titan and Venus.)

(2) One thing which the science definition team recommended strongly for JIMO could perhaps end up flying on this much smaller chemically-propelled mission: a small Europa lander weighing only a few hundred kilograms. It would certainly further complicate the mission -- but, given the very long intervals between Europa missions, we may well want to jump to this phase as fast as possible. (Exobiologist Jack Hunter once told me bitterly: "I'll be in a wheelchair by the time they land on Europa.") The Roadmap mentions it briefly as a possible addition -- and there was a very detailed design study done last year ( http://dosxx.colorado.edu/%7Ebagenal/OPAG/...port_Final2.pdf ).

It would use a flat-out full soft-landing system rather than airbags or other shock absorbers, on the grounds that the latter are just too heavy. Its two mandatory instruments would be a seismometer (to probe the thickness of the ice layer) and a mass spectrometer hooked up to a system for separating out various organic compounds (probably using liquid rather than gas chromatography) from the ice. The next two priority instruments would be a magnetometer (for more data on the ice layer thickness), and a surface camera -- that's probably as much as they could cram onto it. But the catch is whether they can design a lightweight sampling system for the mass spectrometer that could penetrate deep enough into the ice to get below the upper layer of Europan regolith where any biological organics have been unrecognizably scrambled by Jupiter's radiation -- probably a couple of meters. If they can't, I don't think a piggyback lander is worth flying.

But, with a lander or not, I think Europa Orbiter is finally definitely going to fly -- quite posibly as a collaboration with the ESA, which has recently officially declared itself very interested in such a teamup. NASA has finally been forced to get serious about this mission, as they finally were with the Pluto probe.