[X] My Assistant

[ljk4-1]

Paper: astro-ph/0510798

Date: Fri, 28 Oct 2005 10:23:28 GMT (316kb)

Title: Modeling the Jovian subnebula: II - Composition of regular satellites
ices

Authors: Olivier Mousis and Yann Alibert

Comments: 9 pages, A&A, in press
\\
We use the evolutionary turbulent model of Jupiter's subnebula described by
Alibert et al. (2005a) to constrain the composition of ices incorporated in its
regular icy satellites. We consider CO2, CO, CH4, N2, NH3, H2S, Ar, Kr, and Xe
as the major volatile species existing in the gas-phase of the solar nebula.
All these volatile species, except CO2 which crystallized as a pure condensate,
are assumed to be trapped by H2O to form hydrates or clathrate hydrates in the
solar nebula. Once condensed, these ices were incorporated into the growing
planetesimals produced in the feeding zone of proto-Jupiter. Some of these
solids then flowed from the solar nebula to the subnebula, and may have been
accreted by the forming Jovian regular satellites. We show that ices embedded
in solids entering at early epochs into the Jovian subdisk were all vaporized.
This leads us to consider two different scenarios of regular icy satellites
formation in order to estimate the composition of the ices they contain. In the
first scenario, icy satellites were accreted from planetesimals that have been
produced in Jupiter's feeding zone without further vaporization, whereas, in
the second scenario, icy satellites were accreted from planetesimals produced
in the Jovian subnebula. In this latter case, we study the evolution of carbon
and nitrogen gas-phase chemistries in the Jovian subnebula and we show that the
conversions of N2 to NH3, of CO to CO2, and of CO to CH4 were all inhibited in
the major part of the subdisk. Finally, we assess the mass abundances of the
major volatile species with respect to H2O in the interiors of the Jovian
regular icy satellites. Our results are then compatible with the detection of
CO2 on the surfaces of Callisto and Ganymede and with the presence of NH3
envisaged in subsurface oceans within Ganymede and Callisto.

\\ ( http://arXiv.org/abs/astro-ph/0510798 , 316kb)

[Guest_BruceMoomaw_*]

There has already been a lot of interest in a solar-powered Trojan flyby mission -- maybe even one that flies by more than one Trojan -- which could very likely be made within the Discovery cost cap. Beth Ellen Clark of Cornell was associated with one such Discovery proposal called "Andromache", although it's hard to find anything on it.

But: there is also now a proposal floating around -- neat acronym and all -- to actually have a New Frontiers-class craft orbit one or maybe even two Trojans. It's called PARIS; it would use the new concept of a low-powered but long-duration ion drive powered by a particularly large 1-kilowatt RTG (which must use the new, more efficient future RTG designs to reduce its plutonium load); and there have already been at least two abstracts on it, the most recent being at http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1922.pdf . (This new type of propulsion system is attracting increasing interest; it would apparently also allow a relatively low-cost giant planet orbiter which could do an awful lot of putt-putting around the planet's system of moons -- including orbiting one or more of them -- after the orbiter was initially braked into orbit around the planet by aerocapture.)

[nprev]

There has already been a lot of interest in a solar-powered Trojan flyby mission -- maybe even one that flies by more than one Trojan -- which could very likely be made within the Discovery cost cap.  Beth Ellen Clark of Cornell was associated with one such Discovery proposal called "Andromache", although it's hard to find anything on it.

But: there is also now a proposal floating around -- neat acronym and all -- to actually have a New Frontiers-class craft orbit one or maybe even two Trojans.  It's called PARIS; it would use the new concept of a low-powered but long-duration ion drive powered by a particularly large 1-kilowatt RTG (which must use the new, more efficient future RTG designs to reduce its plutonium load); and there have already been at least two abstracts on it, the most recent being at  http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1922.pdf .  (This new type of propulsion system is attracting increasing interest; it would apparently also allow a relatively low-cost giant planet orbiter which could do an awful lot of putt-putting around the planet's system of moons -- including orbiting one or more of them -- after the orbiter was initially braked into orbit around the planet by aerocapture.)

Thanks, Bruce. Should've known that the planetary science community was all over it already...which is a good thing! This would be an exciting and important mission.

[ljk4-1]

Review: Europa, the Ocean Moon

Thu, 16 Feb 2006 - Our five senses are all we have to allow our brains to interact with the world outside our bodies. Space exploration relies almost entirely on one, the sense of sight. Space probes send us images of planets, moons and other objects which we then have to decipher as best we can.

Richard Greenberg in his book Europa, The Ocean Moon uses recent images of Europa, together with our understanding of celestial mechanics and plate tectonics, to unravel this little moon's mysteries. For Europa's biggest mystery is whether it harbours life who may be looking right back at us from their own little world.

http://www.universetoday.com/am/publish/bo...on.html?1622006

[vexgizmo]

Huh... Here's another review, from Mike Belton, leader of the Galileo Imaging Team.

Excerpts:

The descriptions of how Greenberg developed,
promoted, and defended his ideas is another significant part of
the book and one that I find at times to be absurd, generally
irreverent, and, in professional terms, possibly approaching
suicidal.

...

Paranoia is not a word to be used lightly, but there is much that I
am certain is delusional in this aspect of the book. We see this
even in the preface (though there similar instances
throughout the book): “I never felt welcomed by the team…
Then, when it became clear that my field was the key to
understanding what we saw at Europa and evident how
significant those discoveries were, attempts to keep me
marginalized were driven by transparent social, political, and
financial motives.” This is absurd. The book is filled with
words and phrases like: “professional gladiators,” “powerful
infighters,” “perverted definition of ‘team’,” “sycophantic,”
“hustlers,” “enforcers,” “malignity, envy, and ignorance,”
“locked out,” “pontificating,” “jealousy,” and “animosity.”
Nowhere, as far as I can see, do the concepts on which the
everyday world of our profession is based, that is, integrity,
trust, and skeptical inquiry, get a fair shake. Even the players
who are mentioned by name are stereotyped. Those who
worked with the author are uniformly brilliant and insightful;
those who question or raise opposing ideas are to one degree
or another vilified. As I noted before: this is absurd.

Attached File(s)

 BeltonOnGreenberg.pdf ( 287.37K ) Number of downloads: 380