archive: SETI CCNet DIGEST 02/02/99
SETI CCNet DIGEST 02/02/99
Larry Klaes ( lklaes@bbn.com )
Tue, 02 Feb 1999 09:45:10 -0500
>From: Benny J Peiser <b.j.peiser@livjm.ac.uk>
>Sender: humbpeis@livjm.ac.uk
>To: cambridge-conference@livjm.ac.uk
>Subject: CCNet DIGEST 02/02/99
>Date: Tue, 2 Feb 1999 10:21:17 -0500 (EST)
>Priority: NORMAL
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>CCNet DIGEST, 2 February 1999
>------------------------------
>
> QUOTE OF THE DAY
> (from Larry Klaes <lklaes@BBN.COM>)
>
> Doubt thou the stars are fire;
> Doubt that the sun doth move;
> Doubt truth to be a liar;
> But never doubt I love.
>
> William Shakespeare, Hamlet II.ii
>
>
>(1) THE CCNet SURVEY: A REMINDER
> Benny J Peiser <b.j.peiser@livjm.ac.uk>
>
>(2) ATEN-TYPE ASTEROID 1991 VE AND MERCURY
> Piero Sicoli and Manca Franscesco <sormano@tin.it>
>
>(3) WHERE'S ZE MONEY?
> Michael Paine <mpaine@tpgi.com.au>
>
>(4) DECIPHERING PHOLUS
> Bernd Pauli <bernd.pauli@lehrer1.rz.uni-karlsruhe.de>
>
>(5) NEAR - THE CONNECTION WITH METEORITES
> Bernd Pauli <bernd.pauli@lehrer1.rz.uni-karlsruhe.de> wrote:
>
>(6) TIDAL DISRUPTION OF STRENGTHLESS RUBBLE PILES
> J.M. Hahn*) & T.W. Rettig, LUNAR & PLANETARY INST
>
>(7) MODELLING THE EVOLUTION OF THE SPACE DEBRIS POPULATION
> A. Rossi et al., CNR, PISA,ITALY
>
>(8) THE EFFECTS OF METEOROID STREAM ENHANCED ACIVITY ON HUMAN SPACE
> FLIGHT
> G. Cevolani*) & L. Foschini, CNR,BOLOGNA,ITALY
>
>(9) STARDUST SCHEDULED FOR LAUNCH TO RENDEZVOUS WITH COMET
> Andrew Yee <ayee@nova.astro.utoronto.ca>
>
>(10) ICE CORES REVEAL LONG-RANGE GREENLAND CLIMATE VARIABILITY
> Geophysical Research Letters <jupiter@agu.org>
>
>
>=====================
>(1) THE CCNet SURVEY: A REMINDER
>
>>From Benny J Peiser <b.j.peiser@livjm.ac.uk>
>
>A big thank you to all of those 155 list members who have returned
>completed questionnaires, some of which with extensive comments
>and suggestions. I intend to post the results of the survey
>together with a wide selection of comments early next week.
>
>I won't spill the beans, but I can tell list members already that there
>will be some changes to the CCNet format (not to its features) which
>should satisfy the wishes and requests of the vast majority of
>subscribers. In particular, it is planned that subscribers will be able
>to choose between various options in order to deselect those services
>they no longer wish to receive.
>
>For subcribers who still intend to return completed questionnaires or
>who failed to notice it last Friday, I will post the form once again
>today (please ignore the questionnaire if you have already completed
>it).
>
>Benny J Peiser
>
>=================
>(2) ATEN-TYPE ASTEROID 1991 VE AND MERCURY
>
>>From Piero Sicoli and Manca Franscesco <sormano@tin.it>
>
>A numerical integration of the orbit of asteroid 1991 VE has shown that
>it has repeated close approaches to Mercury, and therefore has stirred
>our interest about this object. During the recent favourable opposition
>(January 1999) the asteroid was included in the observing schedules of
>several observatories (including our own); a new computation, based on
>the improved orbit, confirms that 1991 VE has at least 9 encounters to
>Mercury (within 0.021 AU) during the next 200 years. Next approach
>(0.006 AU) will happen on October 23, 2006, but a closer one seems to
>have occurred at the beginning of this century (0.004 AU, on April 7,
>1909).
>
>Our list of close encounters between asteroids and planets (recently
>updated) is available at:
>
>http://www.brera.mi.astro.it/sormano/pcel.html
>
>Piero Sicoli and Francesco Manca
>Sormano Astronomical Observatory
>E-Mail: Sormano@tin.it
>WWW : http://www.brera.mi.astro.it/sormano/
>
>===================
>(3) WHERE'S ZE MONEY?
>
>>From Michael Paine <mpaine@tpgi..com.au>
>
>Dear Benny,
>
>[You will probably get swamped with email about this!] NASA has posted
>a summary of its FY2000 budget on the internet
>http://www.nasa.gov/budget/budget_index.html
>
>I couldn't find a mention of the funding for NEO research anywhere in
>the $13.5 Billion of expenditure!
>
>Michael Paine
>
>========================
>(4) DECIPHERING PHOLUS
>
>>From Bernd Pauli <bernd.pauli@lehrer1.rz.uni-karlsruhe.de>
>
>>From Sky & Telescope, March 1999, p. 29):
>
>A team led by Dale P. Cruikshank (NASA/Ames Research Center) believes
>the large, distant "asteroid" 5145 Pholus fits the composition of "a
>giant comet nucleus that is not, and may never have been, active. " In
>the October 1998 issue of lcarus, Cruikshank's group shows that Pholus
>is a close spectral match to an object covered in most places by
>amorphous carbon and elsewhere by a mixture of tiny silicate grains,
>water ice, frozen methanol (CH3OH), and complex organic matter. The
>silicate mineral forsterite (Mg2SiO4) was the key to a good fit; this
>form of olivine is commonly observed in the dust clouds around other
>stars. Traveling in a highly elongated orbit with a mean heliocentric
>distance of 20.2 astronomical units (3.02 billion kilometers), Pholus
>is a 190 km-wide member of the Centaurs objects considered escapees
>from the distant Kuiper Belt. It was discovered in 1992 and shortly
>thereafter found to be one of the solar system's reddest objects (S&T:
>January 1993, page 15).
>
>Copyright 1999, Sky & Telescope
>
>=========================
>(5) NEAR - THE CONNECTION WITH METEORITES
>
>>From Bernd Pauli <bernd.pauli@lehrer1.rz.uni-karlsruhe.de> wrote:
>
>>From Astronomy, February 1999, p. 59:
>
>Scientists hope NEAR’s close look at Mathilde and Eros will solve one
>of the biggest mysteries of asteroid and meteorite study: To what
>asteroid class do meteorites belong? Scientists think that nearly all
>meteorites were once parts of asteroids, and collisions broke off
>pieces and changed their orbits to ones intercepting Earth. Although
>the S and C classifications make up almost 75 percent of all known
>asteroids, the spectrum of neither type corresponds very closely to
>most meteorites found on Earth. ln fact, only a handful of asteroids
>fit precisely the spectral class of 90 percent of all known meteorites.
>Even more puzzling, the closer you get to Earth, the worse the match. C
>asteroids, orbiting from the middle of the asteroid belt outward, match
>only poorly. S asteroids, orbiting from the middle of the asteroid belt
>inward, match not at all. While almost all near-Earth asteroids belong
>to the S class, only 10 percent of meteorites found on Earth resemble
>these asteroids even vaguely. In many ways the study of asteroids today
>is comparable to the study of the major planets in 1968. Before the
>first orbital missions to Mars and Venus, most of our knowledge of the
>planets was based on their telescopic appearance and spectra. Our only
>good views had been limited to a few quick flybys, mere glimpses by a
>handful of spacecraft. Overall we knew little and understood less.
>Similarly, other than the tantalizing glimpses provided by the NEAR and
>Galileo spacecraft, we have not yet seen an asteroid in detail.
>Astronomers have approximated the make-up and shape of these mysterious
>objects, but without actually looking at them close up, we can't really
>know what they are. This should all change in 1999, as NEAR slips into
>orbit around Eros and begins to pick at its mysteries. (Robert
>Zimmermann)
>
>Copyright 1999, Astronomy Magazine
>
>=========================
>(6) TIDAL DISRUPTION OF STRENGTHLESS RUBBLE PILES
>
>J.M. Hahn*) & T.W. Rettig: Tidal disruption of strengthless rubble
>piles - a dimensional analysis. PLANETARY AND SPACE SCIENCE, 1998,
>Vol.46, No.11-12, pp.1677-1682
>
>*) LUNAR & PLANETARY INST,3600 BAY AREA BLVD,HOUSTON,TX,77058
>
>A relatively simple prescription for estimating the number of debris
>clumps n that form after a catastrophic tidal disruption event is
>presented. Following the breakup event, it is assumed that the
>individual debris particles follow keplerian orbits about the planet
>until the debris' gravitational contraction timescale t(c) becomes
>shorter than its orbital spreading timescale t(s). When the two
>timescales become comparable, self-gravity breaks up the debris
>train into n similar to L/D clumps, which is the debris length/diameter
>ratio at that instant. The clumps subsequently orbit the planet
>independent of each other. The predicted number of clumps n is in good
>agreement with more sophisticated N-body treatments of tidal breakup
>for parabolic encounters, and the dependence of n upon the progenitor's
>density as well as its orbit is also mapped out for hyperbolic
>encounters. These findings may be used to further constrain both the
>orbits and densities of the tidally disrupted bodies that struck
>Callisto and Ganymede. A cursory analysis shows that the Gomul and
>Gipul crater chains on Callisto, which have the greatest number of
>craters among the known chains, were formed by projectiles having
>comet-like densities estimated at rho(0) less than or similar to 1
>gm/cm(3). (C) 1998 Elsevier Science Ltd. All rights reserved.
>
>====================
>(7) MODELLING THE EVOLUTION OF THE SPACE DEBRIS POPULATION
>
>A. Rossi*), L. Anselmo, A. Cordelli, P. Farinella, C. Pardini: Modelling
>the evolution of the space debris population. PLANETARY AND SPACE
>SCIENCE, 1998, Vol.46, No.11-12, pp.1583-1596
>
>*) CNR,CNUCE,I-56126 PISA,ITALY
>
>The current space activities are already disturbed and jeopardized by
>the growing number of orbiting debris. Those planned for the near
>future, such as the launch of large satellite constellations and the
>construction of the international space station, are even more
>sensitive to the evolution of the space environment. Therefore, a clear
>picture of the present situation in Earth orbit and its future
>evolution is needed. In this paper we describe in some details
>the work we have carried out on this problem in the last several years.
>Starting from the current population and simulating a reasonable
>scenario for the space activities in the next decades, we have obtained
>plausible quantitative models of the possible future space environment.
>We summarize some results concerning the effectiveness of possible
>mitigation measures and assess the robustness of these results, by
>checking how sensitively they depend upon the initial conditions and
>the choice of some model parameters. We also analyze the effect of the
>launch of a number of satellite constellations, showing the importance
>of the adoption of some debris prevention measures in their launch
>policies. Finally, we study the possible problems arising from the
>recent discovery of a new family of debris composed by drops of NaK
>coolant, that leaked outside the nuclear reactors of the Soviet
>RORSAT-class satellites. Our preliminary results indicate that these
>drops are going to cause an increasing number of small-scale, possible
>satellite-damaging impacts but, due to their small size, no additional
>catastrophic collisions; therefore their influence on the long-term
>evolution of the overall debris population is limited. (C) 1998
>Elsevier Science Ltd. All rights reserved.
>
>================
>(8) THE EFFECTS OF METEOROID STREAM ENHANCED ACIVITY ON HUMAN SPACE
> FLIGHT
>
>G. Cevolani*) & L. Foschini: The effects of meteoroid stream enhanced
>activity on human space flight: an overview. PLANETARY AND SPACE
>SCIENCE, 1998, Vol.46, No.11-12, pp.1597-1604
>
>*) CNR,IST FISBAT,VIA GOBETTI 101,I-40129 BOLOGNA,ITALY
>
>The origin, dispersion mechanisms and evolution of particle streams
>producing enhanced activity (outburst or storm) of meteoroids are
>discussed in relation to their effects on artificial satellites and
>space platforms. A review of the active meteoroids suggests that at
>least five streams may undergo outburst or storm activity in the next
>few years. Modern radio techniques not affected by illumination
>conditions and cloud coverage, improve significantly the detectability
>of meteor streams. The impact probabilities of storm meteoroids on
>space platforms in Earth orbit can increase by factors in excess of
>10(2)-10(4) over the sporadic background. (C) 1998 Elsevier Science
>Ltd. All rights reserved.
>
>======================
>(9) STARDUST SCHEDULED FOR LAUNCH TO RENDEZVOUS WITH COMET
>
>>From Andrew Yee <ayee@nova.astro.utoronto.ca>
>
>University of Washington
>
>FROM: Vince Stricherz
>206-543-2580
>vinces@u.washington.edu
>
>FOR IMMEDIATE RELEASE: Feb. 1, 1999
>
>UW astronomy professor's Stardust quest set for launch Saturday
>
>It's a moment University of Washington astronomy professor Donald
>Brownlee has been awaiting for nearly two decades. If all goes as
>planned, that moment will arrive Saturday afternoon when a Boeing Delta
>II rocket, with "University of Washington" emblazoned on the side,
>sends a desk-sized spacecraft on a seven-year journey to rendezvous
>with a comet.
>
>Stardust is scheduled to launch from Cape Canaveral, Fla., at 1:07 p.m.
>PST, and UWTV will provide live coverage. The mission, selected in 1995
>by NASA as part of its Discovery series, aims to capture particles from
>comet Wild 2 (pronounced Vilt 2) and return them to Earth for analysis
>in laboratories at the UW, NASA and around the world. There's much to
>be learned, Brownlee said.
>
>"People have long suspected that comets played a role in the origin of
>life. No one really knows this because no one knows how life began. But
>we do know that comets are the most carbon-rich materials in the solar
>system, and we know they're full of organic compounds and they fall on
>the Earth all the time. Even now we have tens of thousands of tons of
>comet particles landing on the Earth every year," he said.
>
>Even though microscopic comet particles blanket open spaces such as
>parks and football stadiums every year, those particles don't tell the
>same story as ones collected from a comet such as Wild 2, Brownlee
>said. That's because Wild 2 only recently started orbiting close enough
>to the sun to make the mission feasible, so there hasn't been time
>enough for the sun's heat to destroy the characteristics of particles
>that have been preserved in a cryogenic deep freeze of space for
>billions of year.
>
>In 1980, Brownlee and NASA first considered a mission to capture comet
>particles. In that case, the target would have been Halley's comet, but
>the idea proved unworkable. Various technological advances and a bit of
>celestial luck changed that. Before 1974, Wild 2 traveled outside the orbit
>of Jupiter. But a close encounter with Jupiter that year altered the
>comet's trajectory, bringing it close enough to make Stardust possible.
>The spacecraft's encounter with the comet in early 2004 will take place
>just outside the orbit of Mars, 242 million miles from Earth on the
>other side of the sun.
>
>The mission is the first since Apollo 17 in 1972 to return
>extraterrestrial samples to Earth, and it is the first to bring back
>samples from beyond the orbit of the moon. Scientists will study the
>returned comet particles in the hope of understanding how life evolved
>on Earth. The planet probably was formed without water and without
>carbon or nitrogen, the building blocks of life. "The building blocks
>of life have long been thought to have come from further out in the
>solar system, out further away from the sun, and these would be
>materials from asteroids and comets," Brownlee said.
>
>Stardust will have journeyed 3.1 billion miles before it parachutes
>into the Utah desert in early 2006. During its encounter with Wild 2, a
>tennis-racquet shaped collector, sheathed with a wispy substance called
>aerogel, will be extended to collect comet grains when the spacecraft
>is within 100 miles of the comet's icy core. A high-power antenna will
>transmit close-up pictures, and sensitive equipment will gather data
>about the comet.
>
>The mission is a collaboration of the UW, NASA, NASA's Jet Propulsion
>Laboratory at the California Institute of Technology in Pasadena,
>Calif., and Lockheed Martin Astronautics in Denver. Other key members
>of the team are The Boeing Co., Germany's Max-Planck-Institut fuer
>extraterrestrische Physik, the NASA Ames Research Center and the
>University of Chicago.
>
>Brownlee expects information gathered by Stardust to shed light on how
>the solar system and the universe evolved. The mission also could have
>implications on astrobiology, the search for life beyond Earth. The UW
>this fall will begin the first doctoral program in astrobiology to
>train people to look for life on other celestial bodies, such as Mars
>and Europa, a moon of Jupiter.
>
>"From the astrobiology standpoint, we're interested in what kind of
>organic materials actually exist and how much there is and whether this
>played a role (in the formation of life)," Brownlee said. "Now this may
>be an impossible problem. We can study astrobiology and we can
>investigate how life might have formed, but no one was there taking
>notes when life formed.
>
>"You have things ... before there was life and things after there was
>life but the real records aren't there," he said. "But by insight on
>this, you can at least look at what the starting materials were. So
>that's what Stardust is going to do, look at the starting materials,
>what was around in the solar system before life existed on Earth."
>
>The name "Stardust" seemed appropriate because of the nature of the
>project and the fact that people can relate to that name, Brownlee
>said. A recent radio interview ended with a few bars of the song
>"Woodstock" by Joni Mitchell, which includes the lyrics: "We are
>stardust, we are golden, we are billion-year-old carbon." That's an
>appropriate thought, Brownlee said.
>
>"Comets are a vehicle that brings organic materials to the Earth. Many
>of the carbon atoms in our bodies were in comets early in the history
>of the solar system. So one of the bylines of the Stardust mission is
>that we are stardust. Our bodies are actually made of stardust."
>
>Science aside, there's a hint of romanticism about this mission. That's
>why, come Saturday, it won't be "Woodstock" but instead the soft
>strains of Hoagy Carmichael's "Stardust" drifting through the launch
>area.
>
>###
>
>Additional information is available at http://stardust.jpl.nasa.gov or
>at http://www.washington.edu/newsroom/stardust/stardust.html
>
>================
>(10) ICE CORES REVEAL LONG-RANGE GREENLAND CLIMATE VARIABILITY
>
>>From Geophysical Research Letters <jupiter@agu.org>
>
>Ice cores from the Greenland Ice Sheet date as far back to 110 kyr b.p.
>and are useful for examining fluctuations in chemical and physical
>characteristics on various time scales. Kahl et. al. ["Decadal-scale
>variability in long-range atmospheric transport to the summit of the
>Greenland Ice Sheet"] find an association between long-range
>atmospheric transport to the Greenland Ice Sheet and large-scale
>climate variability on the annual to decadal time scales. This
>demonstrates that climate variations far upstream of Greenland can
>influence the contributions of material from specific remote areas to
>the ice sheet. Using a 44-year set of 10-day modeled air trajectories
>arriving daily at Summit, Greenland, the authors show that many
>trajectories with long residence times at the 500 hPa and 700 hPa
>levels correlate significantly with the Pacific/North American pattern,
>the Southern Oscillation and the North Atlantic Oscillation.
>
>----------------------------------------
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