N'joy, after the deep impact

"We used to be afraid of comets. The dinosaurs should have been afraid of
comets. Now it is the comet's turn to be afraid."

Dr Andrew Coates
Mullard Space Science Laboratory at UCL



Arvind
. ... ..... ....... ........... ............. .................

Arvind Paranjpye

Sci./Tech. Officer
Public Outreach Programme
Inter-University Centre for Astronomy and Astrophysics
Post Bag #4, Ganeshkhind, Pune 411 007 - India

Phone +91 20 2560 4100 (operator) :: Fax +91 20 2560 4699

2560 4601 (direct office)
2560 4303 (direct lab)
2560 4421 (direct home)


URL http://www.iucaa.ernet.in/~arp

=== . = ==== = ===== ========= == ====== . . . . . . . . . . . .



But it's actually from Dr Andrew Coates (Mullard Space Science Laboratory
at UCL: Best regards
Benny

P.S. Have you got a list of Indian science writers and journalists who
might be interested in CCNet?


> -----Original Message-----
> From: arp@... [mailto:arp@...]
> Sent: 04 July 2005 11:57
> To: Peiser, Benny
> Subject: Re: CCNet: WE USED TO BE AFRAID OF COMETS - NOW ITS
> THEIR TURN
> TO
>
>
> Dear Benny Peiser,
>
> is "WE USED TO BE AFRAID OF COMETS - NOW ITS THEIR TURN TO BE
> AFRAID OF US"
> your quote?
>
> One of the best.
>
> Local news paper guy saw this and might quote you on this.
>
> Regards
>
> Arvind Pranjpye
> . ... ..... ....... ........... ............. .................
>
> Arvind Paranjpye
>
> Sci./Tech. Officer
> Public Outreach Programme
> Inter-University Centre for Astronomy and Astrophysics
> Post Bag #4, Ganeshkhind, Pune 411 007 - India
>
> Phone +91 20 2560 4100 (operator) :: Fax +91 20 2560 4699
>
> 2560 4601 (direct office)
> 2560 4303 (direct lab)
> 2560 4421 (direct home)
>
>
> URL http://www.iucaa.ernet.in/~arp
>
> === . = ==== = ===== ========= == ====== . . . . . . . . . . . .
>
>
>
> > CCNet 86/2005 - 4 July 2005
> > WE USED TO BE AFRAID OF COMETS - NOW ITS THEIR TURN TO BE
> AFRAID OF US
> >
> ----------------------------------------------------------------------
> >
> >
> > After 172 days and 268 million miles of deep space stalking, Deep
Impact successfully reached out and touched comet Tempel 1. The
collision between the coffee table-sized impactor and city-sized comet
occurred at 1:52 am EDT.
> > --Nasa News, 4 July 2005
> >
> >
> >
> > What a way to kick off America's Independence Day. The challenges of
this mission and teamwork that went into making it a success, should
make all of us very proud.
> > --Rick Grammier, JPL, 4 July 2005
> >
> >
> >
> > How a washing-machine sized impactor could produce such a large
disturbance
> > is going to take some explanation.
> > --Don Yeomans, JPL, 4 July 2005
> >
> >
> > We used to be afraid of comets. The dinosaurs should have
> been afraid
> > of comets. Now it is the comet's turn to be afraid.
> > --Andrew Coates, Mullard Space Science Laboratory, UCL
> >
> >
> > (1) DEEP IMPACT KICKS OFF FOURTH OF JULY WITH DEEP SPACE FIREWORKS
> > NASANews@...
> >
> > (2) DEEP IMPACT SMASHES ALL EXPECTATIONS
> > David L Chandler, New Scientist, 4 July 2005
> >
> > (3) NASA'S DEEP IMPACT MISSION PROJECTILE STRIKES COMET
> > Bloomberg, 4 July 2005
> >
> > (4) COULD COMET TEMPEL 1 HARBOR THE SEEDS OF LIFE?
> > Kate Melville <kate_e_melville@...>
> >
> > (5) PHYSICAL PROPERTIES OF ASTEROID ITOKAWA: TARGET OF THE
> HAYABUSA SAMPLE
> > RETURN MISSION
> > Icarus. Volume 176, Issue 2 , August 2005, Pages 408-417
> >
> >
> > ============(1) DEEP IMPACT KICKS OFF FOURTH OF JULY WITH DEEP SPACE
FIREWORKS
> >
> > NASANews@...
> >
> > Dolores Beasley
> > Headquarters, Washington
> July 4, 2005
> > (Phone: 202/358-1753)
> >
> > DC Agle
> > Jet Propulsion Laboratory, Pasadena, Calif.
> > (Phone: 818/393-9011)
> >
> > Lee Tune
> > University of Maryland, College Park
> > (Phone: 301/405-4679)
> >
> > RELEASE: 05-250
> >
> > DEEP IMPACT KICKS OFF FOURTH OF JULY WITH DEEP SPACE FIREWORKS
> >
> > After 172 days and 268 million miles of deep space
> stalking, Deep
> > Impact successfully reached out and touched comet Tempel 1. The
collision between the coffee table-sized impactor and
> city-sized comet
> > occurred at 1:52 am EDT.
> >
> > "What a way to kick off America's Independence Day," said
> Deep Impact
> > project manager Rick Grammier of NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "The challenges of this mission and
> teamwork that went
> > into making it a success, should make all of us very proud."
> >
> > "This mission is truly a smashing success," said Andy Dantzler,
director of NASA's Solar System Division. "Tomorrow and in the days
ahead we will know a lot more about the origins of our
> solar system."
> >
> > Official word of the impact came 5 minutes after impact
> when, at 1:57
> > am EDT, an image from the spacecraft's medium resolution camera was
downlinked to the computer screens of the mission's science
> team showed
> > the tell-tale signs of a high-speed impact.
> >
> > "The image clearly shows a spectacular impact," said Deep Impact
principal investigator Dr. Michael A'Hearn of the University of
Maryland, College Park. "With this much data we have a long
> night ahead
> > of us, but that is what we were hoping for. There is so
> much here it is
> > difficult to know where to begin."
> >
> > The celestial collision and ensuing data collection by the
> nearby Deep
> > Impact mothership was the climax of a very active 24 hour period for
the mission which began with impactor release at 2:07 am
> EDT on July 3.
> > Deep space maneuvers by the flyby, final checkout of both spacecraft
and comet imaging took up most of the next 22 hours. Then,
> the impactor
> > got down to its last two hours of life.
> >
> > "The impactor kicked into its autonomous navigation mode right on
time," said Deep Impact navigator Shyam Bhaskaran, of JPL. "Our
preliminary analysis indicates the three impactor targeting
> maneuvers
> > occurred on time at 90, 35 and 12.5 minutes before impact."
> >
> > At the moment the impactor was vaporizing itself in its 6.3 miles a
second collision with comet Tempel 1, the Deep Impact flyby
> spacecraft
> > was monitoring events from nearby and will continue to do so for the
next several days.
> >
> > "The flyby surviving closest approach and shield mode has
> put the cap
> > on an outstanding day," said Grammier. "Soon, we will begin
> the process
> > of downlinking all the encounter information in one batch
> and hand it
> > to the science team."
> >
> > Deep Impact will provide a glimpse beneath the surface of a comet,
where material from the solar system's formation remains relatively
unchanged. Mission scientists expect the project will answer basic
questions about the formation of the solar system, by
> offering a better
> > look at the nature and composition of the frozen celestial travelers
known as comets.
> >
> > The University of Maryland is responsible for overall Deep Impact
mission science, and project management is handled by JPL. The
spacecraft was built for NASA by Ball Aerospace & Technologies
Corporation, Boulder, Colo.
> >
> > For information about Deep Impact on the Internet, visit:
> >
> > www.nasa.gov/deepimpact
> >
> > ==========(2) DEEP IMPACT SMASHES ALL EXPECTATIONS
> >
> > New Scientist, 4 July 2005
> > http://www.newscientistspace.com/channel/solar-system/dn7622
> >
> > David L Chandler, Pasadena
> >
> > Comet Tempel 1 has smashed into the Deep Impact probe,
> producing a blast
> > of light that prompted the mission control room at NASA's
> Jet Propulsion
> > Laboratory in California, US, to erupt into cheers and applause.
> >
> > Scientists and engineers jumped in the air, pumped their
> fists and hugged
> > one another. Not only had their mission to deliberately
> collide with a
> > comet for the first time succeeded perfectly, but the
> prospect of a damp
> > squib - with the impactor passing right through a diffuse,
> rubbly comet -
> > had fizzled away.
> >
> > "Geez, and we thought it was going to be subtle," exulted
> JPL scientist
> > Don Yeomans, one of the Deep Impact science team. "That was
> considerably
> > brighter, and had considerably more material coming out, than I had
expected," he said.
> >
> > "We are just ecstatic," said JPL director Charles Elachi of
> the success of
> > the $330 million mission. "It was worth every penny we spent on it."
> >
> > Punching a hole
> >
> > The aim of the cosmic collision was to reveal details about
> the interior
> > of comets. These bodies of ice and dust a few kilometres across are
believed to contain primordial material, preserved in the
> deep-freeze of
> > space, since the formation of the solar system.
> >
> > By punching a hole in the comet's crusty surface to release
> material from
> > below, the mission should reveal details of its composition, through
detailed spectral observations. The size and shape of the
> crater will give
> > information on its structure.
> >
> > One reason for the spectacular burst released by the comet
> on impact could
> > be that puncturing the crust released subsurface pressure,
> allowing a much
> > bigger plume of ejecta to spurt out, Yeomans said. However,
> it will take
> > detailed analysis over the coming days to confirm exactly
> what happened 83
> > million miles from Earth.
> >
> > Perfectly circular
> >
> > Even before the impact itself, the twin spacecraft - the
> impactor itself,
> > and the flyby craft which moved aside to observe it - were
> each returning
> > images far more detailed than any previous images of a
> comet's nucleus.
> > The best previous comet images, taken in 2004 by the
> Stardust mission, had
> > a maximum resolution of 25 metres. That can reveal objects about
one-quarter the size of a football pitch, but the new
> images are sharp
> > enough to show objects as small as a football.
> >
> > The pictures show numerous perfectly circular features,
> which could either
> > be impact craters or sinkholes. They also display long
> linear features and
> > a varied topography of rough areas and one smooth region -
> "everything a
> > geologist would love", Yeomans said.
> >
> > Dozens of observatories on Earth, as well as four in orbit,
> were also
> > watching the comet at the time of impact, and those images
> and spectra
> > will be coming in to JPL in the coming days.
> >
> > "How a washing-machine sized impactor could produce such a large
disturbance is going to take some explanation," Yeomans said.
> >
> > Copyright 2005, New Scientist
> >
> > =========(3) NASA'S DEEP IMPACT MISSION PROJECTILE STRIKES COMET
> >
> > Bloomberg, 4 July 2005
> >
> http://www.bloomberg.com/apps/news?pid=10000103&sid=an1ZPEelpT
> gE&refer=us
> >
> > July 4 (Bloomberg) -- A projectile from NASA's Deep Impact
> spacecraft
> > slammed into the comet Tempel 1, creating a crater that
> scientists hope
> > will shed light on some of the solar system's most
> mysterious objects.
> >
> > The projectile, released from the main Deep Impact
> spacecraft about 24
> > hours earlier, struck the comet at a speed of about 23,000
> miles an hour
> > within 30 seconds of the predicted impact time at 1:52 a.m.
> New York time,
> > National Aeronautics and Space Administration spokesman
> John Sepikas said
> > by phone from Nasa's Jet Propulsion Laboratory in Pasadena,
> California.
> >
> > Scientists believe comets are remnants of the era when the
> solar system
> > began about 4.6 billion years ago and may have delivered
> elements crucial
> > to life on Earth. Mission managers, who only had one shot
> at Tempel 1,
> > hope blowing a hole in a comet will reveal its makeup and
> help show how
> > life started.
> >
> > "We're hoping to gain some insight to answer the question
> of who we are
> > and where we come from," Shadan Ardalan, a mission
> engineer, said in a
> > phone interview from Pasadena. "We believe that billions of
> years ago as
> > planets were forming, comets bombarded our planet, bringing
> in materials
> > that were the building blocks for life."
> >
> > Matter Ejected
> >
> > Images beamed back from the Deep Impact "flyby" spacecraft
> captured the
> > moment of impact, and raw data has already been beamed back
> to Earth,
> > Sepikas said.
> >
> > "The images are spectacular: they captured the explosion," he said.
"Everybody's jumping up and down here."
> >
> > Impact images displayed on NASA's Web site and on NASA TV
> show a bright
> > plume erupting from the comet as the projectile hit it.
> Video taken by the
> > impactor showed the cratered comet drawing closer, with the
> last image
> > beamed back three seconds before the collision.
> >
> > The "ejecta cone" of matter thrown up by the collision was
> at the larger
> > end of predictions, enabling scientists to draw some preliminary
conclusions.
> >
> > "It rules out really porous structures where you tunnel
> very deeply and
> > the impactor slows down gradually," Mike A'Hearn, principal
> investigator
> > for the project and an academic at the University of
> Maryland, said at a
> > press conference aired live on NASA TV. He declined to
> speculate on what
> > conclusions could be drawn from the images about the
> comet's composition.
> >
> > Deep Impact, built by Broomfield, Colorado-based Ball Corp.
> and launched
> > in January, followed the projectile at a distance of about
> 311 miles to
> > watch the collision, aiming its two scientific instruments
> at the comet to
> > look at the crater and any material ejected from it.
> >
> > `New Frontier'
> >
> > Comet Tempel 1, about half the size of Manhattan Island,
> was discovered in
> > 1867 by a German astronomer, Ernst Tempel, while working in
> Marseille,
> > southern France. The comet has an elliptical orbit between Mars and
Jupiter. Deep Impact's probe was about one meter (3.3 feet)
> wide -- about
> > the size of a washing machine.
> >
> > Mission scientists, who before the mission described the
> challenge of
> > hitting the comet as like threading a needle, are now
> processing the data.
> >
> > "This is a new frontier, a great unknown: It's the first
> time anything
> > like this has been attempted, let alone accomplished," Ardalan said.
"Everything performed as flawlessly as could be hoped."
> >
> > The projectile, which was on a "suicide mission," beamed
> data back to the
> > flyby craft until "nearly the point of impact," Ardalan said.
> >
> > Hubble Space Telescope
> >
> > The collision was watched by astronomers and observatories
> on Earth and in
> > space, from the Hubble Space Telescope to the two
> telescopes of the W.M.
> > Keck Observatory atop the Mauna Kea volcano in Hawaii. The
> European Space
> > Agency used instruments aboard its Rosetta ``comet-chaser''
> spacecraft to
> > observe the impact. Rosetta, launched last year, is due to
> send a lander
> > to the surface of the Churyumov-Gerasimenko comet in November 2014.
> >
> > "The impactor was totally vaporized, as per plan, and we
> have a healthy
> > flyby vehicle," Project Manager Rick Grammier said in
> NASA's briefing.
> > Scientists at NASA are due to hold a press conference to
> present further
> > findings at 2 p.m. New York time.
> >
> > The $333 million mission, which shares the same name as a
> 1998 film about
> > a comet striking Earth, may also help NASA determine how to
> attempt to
> > deflect a similar object hurtling toward the planet.
> >
> > There is evidence that an asteroid collision in the Yucatan
> Peninsula may
> > have caused the extinction of the dinosaurs 65 million
> years ago, and many
> > scientists fear another strike is inevitable.
> >
> > `Hurtling Toward Earth'
> >
> > Some fear Deep Impact may send the comet or pieces of it
> hurtling toward
> > Earth, yet managers said the impact would have been akin to
> a bug striking
> > a jetliner and there is no risk to the planet.
> >
> > Arthur C. Clarke first envisioned sending a spacecraft to
> blow a hole in a
> > comet in his 1968 book "2001: A Space Odyssey," yet
> technology limitations
> > have prevented such a mission until now.
> >
> > NASA canceled a plan to send a ship to the comet Korff in
> the mid-1990s
> > and the Deep Impact project was rejected in a different form in 1996
before being approved in 1999.
> >
> > The mission is part of NASA's Discovery program, which is
> designed to
> > improve knowledge of the solar system by exploring planets,
> moons and
> > bodies such as comets and asteroids. The program includes
> missions like
> > Stardust, a spacecraft launched in 1999 that collected
> samples of dust
> > from the comet Wild 2 in January.
> >
> > Deep Impact comes as NASA spacecraft are roaming the
> surface of Mars,
> > circling Saturn and traveling toward Mercury. The mission
> may help the
> > agency fulfill President George W. Bush's space plan, which
> calls for
> > human missions to the moon and Mars as precursors to trips
> into other
> > parts of the solar system.
> >
> > Copyright 2005, Bloomberg
> >
> > ========(4) COULD COMET TEMPEL 1 HARBOR THE SEEDS OF LIFE?
> >
> > Kate Melville <kate_e_melville@...>
> >
> > Hi Benny,
> >
> > I thought you may be interested in an article on our site
> by one of our
> > correspondents. It's quite an interesting read.
> > http://www.scienceagogo.com/news/tempel_seeds.shtml
> >
> > Best regards,
> >
> > Kate
> >
> > ----------
> > Could Tempel 1 Harbor The Seeds Of Life?
> > http://www.scienceagogo.com/news/tempel_seeds.shtml
> >
> > By Rusty Rockets
> >
> > As the July 4 tryst between NASA's Deep Impact spacecraft
> and the comet
> > Tempel 1 draws closer, it might be time to draw breath and
> consider just
> > what may dwell beneath the comet's craggy and gaseous
> surface. Scientists
> > know next to nothing about the composition of a comet's
> nucleus, which is
> > why they are so keen to capture images and analyze the
> post-collision
> > particles and debris. If the mission is successful the
> results could shine
> > a whole new light on the hotly debated topic of panspermia.
> >
> > As something of a preview, the recent images captured by
> Hubble of Tempel
> > 1 show a rare and spectacular flare-up that no doubt comes
> as a welcome
> > sign to many astronomers. "Outbursts such as this may be a
> very common
> > phenomenon on many comets, but they are rarely observed in
> sufficient
> > detail to understand them because it is normally so
> difficult to obtain
> > enough time on telescopes to discover such phenomena," said
> University of
> > Maryland astronomer Michael A'Hearn, who leads the Deep
> Impact mission.
> > "With the information we receive after the impact, it will
> be a whole new
> > ballgame. We know so little about the structure of cometary
> nuclei that
> > almost every moment we expect to learn something new."
> >
> > Make no mistake, the Deep Impact mission may change the way
> scientists
> > look at, not only comets themselves, but how life is
> dispersed across the
> > universe. Panspermia, the idea that comets (and other
> wanderers in space)
> > may be carriers of organic matter and the seeds of life, could be
supported by the findings from the Deep Impact mission.
> Since at this
> > stage nobody can truly claim to be an expert, here are a
> few ideas to
> > consider. What if the comet is a form of communication left
> over from a
> > civilization now long gone? The "message" traveling on the
> comet does not
> > even have to be a sophisticated piece of technology; it
> could be the DNA
> > of a life-form. This isn't as crazy as it sounds and many
> highly regarded
> > scientists from various fields have been working on
> conceptualizing how
> > such non-conventional communication might work. Christopher Rose and
Gregory Wright argued in a paper published in Nature that tangible,
physical objects are far better for interstellar
> communications than using
> > radio signals that need to be constantly repeated and then
> eventually
> > dissipate over long distances anyway. So what about Tempel
> 1 and comets in
> > general as messaging devices? "Comets are one of my
> favorite vehicles for
> > posting a message, even if they might be unlikely for the sorts of
messaging I have in mind. I like the out-gassing of
> material that could
> > be used as a local delivery service only in an inner solar
> system [heat
> > sensitive release] and I like the fact that the associated
> coma calls
> > attention to comets [advertisement of the message]," Dr
> Rose told Science
> > a GoGo.
> >
> > Rose and Wright consider it unlikely that communication
> exchanges between
> > civilizations would ever be a synchronized affair, given
> the vast chasms
> > of time, space and the likely varying technical
> sophistication between
> > civilizations. "If you took, say, 10 million years to reach
> a destination
> > [10,000 light years at a thousandth the speed of light]
> you'd probably
> > want your message to hang around a while - maybe long
> enough for the local
> > denizens to become sophisticated enough to come get the
> message," said
> > Rose. And this is one of the major flaws in the concept of
> a comet being a
> > delivery system. "Comets have one annoying flaw from a messaging
perspective - their orbits are not very stable and decay
> after a few tens
> > of thousands of years."
> >
> > Rose also contemplates why a civilization would want to
> make contact in
> > the first place. He believes it's a case of simple
> self-preservation. It's
> > certainly possible that if humanity were ever facing
> annihilation we might
> > want to consider sending out our own DNA, with a suitable "broth" of
organic chemicals in the hope that it would replicate our
> evolutionary
> > journey elsewhere. "If civilizations at any given stellar
> location are
> > short-lived owing to various sorts of celestial or self-inflicted
calamity, there could be a survival benefit to seeding the
> cosmos with
> > compelling records of a civilization in the hopes that it would be
eventually adopted by other fledgling civilizations [or
> subsumed by older
> > ones]. Perhaps most plausible in this context is literal biological
seeding of likely habitats. Under such assumptions, communicating
civilizations may more likely have been spawned [or
> influenced] by older
> > communicating civilizations at other locations while
> non-communicating
> > civilizations may more likely disappear," said Rose, in a
> supplementary
> > paper to the original one published in Nature.
> >
> > Most scientists have not embraced the concept of life on Earth being
seeded from space, and though plausible, it's generally
> regarded as a
> > far-fetched theory. The inhospitable environment of space
> is one of the
> > stumbling blocks to wider acceptance. Rose told Science a
> GoGo that "if
> > the 'message' were biological seeding, then maybe the
> outgassing which
> > forms the coma would be sufficient to deposit sufficient
> material in a
> > hospitable place - though I've not done the calculation and
> so have doubts
> > about the viability of such a method."
> >
> > Fred Hoyle and Chandra Wickramasinghe, both proponents of
> the panspermia
> > idea, believed living entities like bacteria and viruses
> are in abundance
> > in space, and that this is how Earth was seeded. "I take
> the view that all
> > the genes that we have were already here, and the event
> that added them to
> > the Earth was 570 million years ago. You know, the beginning of the
Cambrian, that great event. And that everything that we
> have subsequently
> > used has been simply a question of permuting and combining
> what came in at
> > that time," said Hoyle in a 1996 interview. Wickramasinghe
> told Science a
> > GoGo that he looked "forward to seeing the results [of the
> Deep Impact
> > mission] with bated breath. I would expect to find more evidence of
organic dust and also of a burnt outer asphalt-like crust.
> While all this
> > will not prove comets as biological niches, it would show that it is
entirely possible."
> >
> > According to NASA, the mission has just entered the
> "encounter phase",
> > five days before the impact with comet Tempel 1, so it's
> unlikely the
> > ground crew coordinating the Deep Impact rendezvous will be
> thinking too
> > much about concepts like panspermia. The impact will occur
> at staggeringly
> > high speeds, Tempel 1 is traveling at 66,880 miles per hour
> compared with
> > the impactor spacecraft's 48,990 miles per hour. The impactor craft
launched from Deep Impact itself will be automated, because
> the sheer
> > speed of events creates too great a communications lag
> between it and
> > ground control. The impactor craft will, during its 24 hours of free
flight, travel over half a million miles and maneuver
> itself directly into
> > the path of the comet. The impactor will execute up to
> three thruster
> > firings to fine-tune its flight path as it closes in on the
> comet nucleus.
> > The first is scheduled 90 minutes before impact, followed
> by a second one
> > 35 minutes before impact and a final firing 12.5 minutes
> before impact.
> > The countdown is on and looks to be a nail biter.
> >
> > Source: Media release - University of Maryland, College Park
> > Media release - NASA
> > Panspermia.org - Fred Hoyle Interview
> > Pics (artist's impressions) courtesy NASA
> >
> > Copyright © 1997 - 2005 Science a Go Go and its licensors.
> All rights
> > reserved.
> >
> > =========(5) PHYSICAL PROPERTIES OF ASTEROID ITOKAWA: TARGET OF THE
HAYABUSA SAMPLE RETURN MISSION
> >
> > Icarus. Volume 176, Issue 2 , August 2005, Pages 408-417
> > http://tinyurl.com/d8sz9
> >
> > Physical properties of Asteroid (25143) Itokawa-Target of
> the Hayabusa
> > sample return mission
> >
> > Stephen C. Lowry a), Paul R. Weissman b), Michael D. Hicks
> b), Robert J.
> > Whiteley c) and Steve Larson c)
> >
> > a) Queen's University, APS Division, Department of Physics
> and Astronomy,
> > Belfast BT7 1NN, UK
> > b) Jet Propulsion Laboratory, MS 183-601, 4800 Oak Grove
> Drive, Pasadena,
> > CA 91109, USA
> > c) Lunar and Planetary Laboratory, University of Arizona, 1626 East
University Boulevard, Tucson, AZ 85721, USA
> >
> > Abstract
> > We present results of a ground-based observational study of
> the Hayabusa
> > mission target near-Earth Asteroid (25143) Itokawa. Our
> data consist of
> > BVRI-filter CCD photometry and low resolution CCD
> spectroscopy, from which
> > the asteroid's rotation period, axial ratio, broadband colors, and
taxonomic classification are derived. Analysis of the
> R-filter lightcurve
> > data shows a synodic rotation period of 12.12±0.02 h,
> consistent with
> > results from other observers. We observed a maximum
> peak-to-peak amplitude
> > of 1.05 magnitudes, which-depending on the taxonomic class
> assumed when
> > correcting for phase angle effects-implies a minimum axial
> ratio of 2.14.
> > The shape of the rotation lightcurves varies considerably
> between data
> > sets due to the changing viewing geometry. The lightcurve
> data from this
> > study has been included in the shape model analysis of
> Kaasalainen et al.
> > (2003 Astron. Astrophys, 405, L29-L32) and the Hapke
> analysis of Lederer
> > et al. (2005 Icarus 173,153-165). Color variations were
> also observed,
> > with the interpolated color indices at lightcurve midpoint being:
(B-V)=0.94±0.05, (V-R)=0.40±0.06, and (V-I)=0.74±0.07. Our
> low resolution
> > Palomar spectra from March 2001 covered a wavelength range
> of 0.3-1.0 ?m.
> > We measured a spectral slope of 9.3±0.3%/100 nm between
> 0.55-0.70 ?m and a
> > deep 1 ?m absorption (equivalent ECAS color: w-x=?0.111±0.003,
v-x=0.031±0.003). Comparison of our spectra with published
> ECAS data from
> > Zellner et al. (1985 Icarus 61, 355-416) indicates that
> this object is
> > most likely of Q- or S-type, similar to ordinary chondrite
> meteorites. Our
> > data are more consistent with a Q-type body when both the
> spectroscopic
> > data and the available BVRI photometry are taken into account.
> >
> > FULL PAPER at http://tinyurl.com/d8sz9
> >
> > doi:10.1016/j.icarus.2005.02.002
> > Copyright © 2005 Elsevier Inc. All rights reserved.
> >
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