PLEASE NOTE:
*
CCNet DIGEST, 14 August 1998
----------------------------
(1) "LIFE ON MARS" KILLED BY IMPACT
Ed Scott <escott@kahana.pgd.hawaii.edu>
(2) MORE DOUBTS ABOUT "LIFE ON MARS"
Andrew Yee <ayee@nova.astro.utoronto.ca>
(3) POSSIBLE IMPACT ON JUPITER?
Wolfgang Czegka <czegka@gfz-potsdam.de>
(4) FIRST IMAGES OF A COMET WITH ADAPTIVE OPTICS
O. Marco et al., PARIS OBSERVATORY
(5) L-APLPHA OBSERVATIONS OF COMET HYAKUTAKE
J.L. Bertaux et al., CNRS
(6) MORE OBSERVATIONS OF COMET HYAKUTAKE
E. Gerard et al., MEUDON OBSERVATORY
(7) CHECHING MOLUCULES ON COMET HYAKUTAKE
J.G.A. Wouterloot et al., UNIVERSITY OF
COLOGNE
(8) CONDENSATIONS OF C2 in COMET HYAKUTAKE
C. Laffont et al., BESANCON OBSERVATORY
(9) X-RAYS FROM COMETS
R. Wegmann et al., MAX PLANCK INSTITUTE OF
ASTROPHYSICS
=======================
(1) "LIFE ON MARS" KILLED BY IMPACT
From Ed Scott <escott@kahana.pgd.hawaii.edu>
Impact heating effects in Martian meteorite ALH84001 were
mistaken for evidence of life.
University of Hawaii researchers claim that all of the carbonate
crystals in the rock
formed during an impact and could not have been deposited by
living organisms.
Meteoritics and Planetary Science (1998) 33, 709-720.
"Carbonates in fractures of martian
meteorite ALH84001: petrologic evidence for impact origin"
by Edward R.D. Scott, Alexander
N. Krot, and Akira Yamaguchi
Carbonates in martian meteorite ALH84001 occur as grains on
pyroxene grain boundaries, in
crushed zones, and as disks, veins, and irregularly shaped grains
in healed pyroxene
fractures. Some carbonate disks have tapered Mg-rich edges and
are accompanied by smaller,
thinner and relatively homogeneous, magnesite microdisks.
Except for the microdisks, all
types of carbonate grains show the same unique chemical zoning
pattern on MgCO3-FeCO3-CaCO3
plots. This chemical characteristic and the close spatial
association of diverse carbonate
types show that all carbonates formed by a similar process.
The heterogeneous distribution
of carbonates in fractures, tapered shapes of some disks, and the
localized occurrence of
Mg-rich microdisks appear to be incompatible with growth from an
externally derived
CO2-rich fluid that changed in composition over time. These
features suggest instead that
the fractures were closed as carbonates grew from an internally
derived fluid and that the
microdisks formed from a residual Mg-rich fluid that was squeezed
along fractures.
Carbonate in pyroxene fractures is most abundant near grains of
plagioclase glass that are
located on pyroxene grain boundaries and commonly contain major
or minor amounts of
carbonate. We infer that carbonates in fractures formed from
grain boundary carbonates
associated with plagioclase that were melted by impact and
dispersed into the surrounding
fractured pyroxene. Carbonates in fractures, including
those studied by McKay et al.
(1996), could not have formed at low temperatures and preserved
mineralogical evidence for
martian organisms.
Press release available at: http://www2.hawaii.edu/~ur/releases.html
-----------------------------------------------------------------------------
Ed
Scott
ph: (808) 956-3955; fax: (808) 956-6322
Hawai'i Institute of Geophysics and Planetology, University of
Hawai'i, Honolulu, HI 96822
Express mail to: Sinclair Library, Rm 6, 2425 Campus Road,
Honolulu, HI 96822.
Life on Mars? Read "Planetary Sciences Research
Discoveries" on line at:
http://www.soest.hawaii.edu/PSRdiscoveries
=====================================
(2) MORE DOUBTS ABOUT "LIFE ON MARS"
From Andrew Yee <ayee@nova.astro.utoronto.ca>
National Science Foundation
Media contact:
Cheryl Dybas
(703) 306-1070/cdybas@nsf.gov
Program contact:
Mike Purdy
(703) 306-1580/mpurdy@nsf.gov
Embargoed until 5 P.M. EDT, August 13, 1998
NSF PR 98-43
CHEMICAL REACTION BELIEVED TO SUPPORT UNDERGROUND MICROBES IS NOW
UNLIKELY:
FINDINGS COULD HAVE IMPLICATIONS FOR LIFE ON MARS AND OTHER
PLANETS
A critical chemical reaction previously thought to support
microbial life deep below
Earth's surface, and possibly on Mars, is in fact highly
unlikely. The findings are
reported in this week's issue of the journal Science by
researchers funded by the National
Science Foundation (NSF)'s Life in Extreme Environments (LeXeN)
program and affiliated with
the University of Massachusetts at Amherst (U. Mass.).
"This is an important step forward in our continuing efforts
to understand the processes
that sustain life deep beneath the earth's surface," says
Mike Purdy, director of NSF's
LeXeN program. "Negative findings like this are as important
as positive ones in their
importance to our understanding of the processes that determine
the limits to life."
It had been generally accepted by scientists that hydrogen gas
produced from rock could
provide energy to support the growth of microorganisms living
below Earth's surface, says
U. Mass. microbiologist Derek Lovley. The hydrogen was thought to
be produced when basalt,
a common form of rock, reacts with water.
However, a research team led by Lovley has found that this
concept is incorrect. Although
hydrogen gas can be produced from basalt under artificial
laboratory conditions, there is
no hydrogen production under the conditions actually found in
Earth's subsurface.
Lovley and his colleagues found that hydrogen could only be
produced from the basalt when
the rock was exposed to acidic conditions -- but environments
containing basalt are never
acidic.
"The idea that hydrogen produced from rocks could support
large subsurface microbial
ecosystems on Earth and possibly other planets was fascinating
and was accepted by most
microbiologists," Lovley says. "Unfortunately, this
concept can not be supported by the
available data."
From analyses of chemical and microbiological data, Lovley and
collaborators Robert
Anderson, U. Mass. graduate student, and Francis Chapelle, a
hydrologist at the U.S.
Geological Survey in South Carolina, suggest that the
microorganisms are probably living on
organic matter associated with the rock, not hydrogen. This
is similar to the way that
microorganisms grow in soil on Earth's surface.
The scientists emphasized that even though the microorganisms
living deep in the Earth may
make a living in a manner similar to that of surface
microorganisms, they may have other
unique characteristics. For example, Lovley's recent research has
demonstrated that
microorganisms from the earth's subsurface can be used to remove
radioactive metals, as
well as hydrocarbons from polluted groundwater.
==============
(3) POSSIBLE IMPACT ON JUPITER?
From Wolfgang Czegka <czegka@gfz-potsdam.de>
[as posted on the meteorite-list]
> Ron Baalke schrieb:
>
> > >Last evening (Thursday) I had a call from
David Levy. He said that
> > >a new dark spot has been seen on Jupiter and
that it is possibly an
> > >impact from a piece of SL9 that missed in
July 1994. He had not
> > >seen the spot as of last evening.
>
Hi,
if somebody is interested in an “older” observation of
short timed black-dark spot,
I´ll annex a Word for Windows 6.0 –file with J.H.
Schroeter´s manuscript of "Beobachtungen
verschiedener schwarzdunkler kleiner Flecken des Jupiters, welche
von sehr kurzer Dauer und
im Verhältnis mit der von Cassini bestimmten Umdrehungszeit des
Jupiters von einer merklich
geschwindern Bewegung erschienen" (Observations of different
small black-dark spots on
Jupiter, which are very short timed and which appearing notable
faster in relation to
Jupiter´s revolution determined by Cassini).
If you are not interested just delete it.
Thanks
Wolfgang
------
SCHROETER, LICHTENBERG AND SOME "SHORTTIMED BLACKISH DARK
SPOTS" ON JUPITER 1785. W.
Czegka, Karlsbader Ring 7, D-68782 Brühl, Baden, Germany (czegka@gfz-potsdam.de)
Meteoritics & Planetary Science 32 (1997), A33-34
Looking back on the Shoemaker-Levy 9 Impact on Jupiter (July
1994) it may be desirable to
draw attention on an observation made nearby 200 years before. At
April 30th 1786 JOHANN
HIERONYMUS SCHROETER wrote his first report on observations he
has made between October
26th 1785 and February 26th 1786 on Jupiter at his new Herschel
equipped observatory at
Lilenthal (near Bremen). The original longwinded title of his
manuscript was named:
"Beobachtungen verschiedener schwarzdunkler kleiner Flecken
des Jupiters, welche von sehr
kurzer Dauer und im Verhältnis mit der von Cassini bestimmten
Umdrehungszeit des Jupiters
von einer merklich geschwindern Bewegung erschienen"[1].
Together with a letter [2]
SCHROETER send his manuscript including 3 sketches [Fig.1] to
G.C. LICHTENBERG for a
scientific review. This manuscript should be forwarded by
LICHTENBERG to the Göttingen
Academy of Sciences (Königliche Societät der Wissenschaften zu
Göttingen). Fig.1
Illustration of the "blackish dark" spots on Jupiter
from the french edition [4]
Lichtenberg as we know from correspondence [3] was not filled
with enthusiasm, but he
recommends to SCHROETER to publish a shortened manuscript in
French [4]. Independently
SCHROETER submitted a short version of his manuscript to J. BODE
in Berlin, who published
it in the same year [5]. None of these contemporary articles
achieved the exactness and
brilliance of observation of the original manuscript. LICHTENBERG
never forwarded it, it
was never published, but he kept the manuscript till his death
1799. The next notice we
knew is its mention in the auction-catalogue of LICHTENBERGs
estate [6]. The manuscript was
within the 163 Books which were bought by the University Library.
There GRESKY recovered it
[7]. The manuscript was transcribed by Dieter GERDES [8]. Only
the original sketches were
lost, but we can reconstruct them out of the figures published in
[4]. In 1992 the
transcript was published [9] without any commentary to the
scientific content. Because of
the nearby inaccessibility of the transcript printed in the
“Lichtenberg- Jahrbuch für
1992” in following some detailed citations from the
transcript are reprinted and
commented. The long title of the original manuscript contains as
single of all versions [4,
5] the expression “..schwarzdunkle[r] Flecken von sehr
kurzer Dauer...”:
"Beobachtungen verschiedener schwarzdunkler kleiner Flecken
des Jupiters, welche von sehr
kurzer Dauer und im Verhältnis mit der von Cassini bestimmten
Umdrehungszeit des Jupiters
von einer merklich geschwindern Bewegung erschienen.
von Johann Hieronymus Schroeter
- Viele und oft wiederholte Beobachtungen der jenigen
Veränderungen, welche sich auf den
Oberflächen der Planeten zu ereignen scheinen, können uns
vielleicht mit der Zeit
wichtigere aufgeklärte Begriffe von der bewunderungswürdigsten
Verschiedenheit geben, womit
der Schöpfer die Naturkräfte in anderen Weltkörpern geordnet
hat, und analogische und oft
zu weit getriebene Schlüsse und Vorutheile zerstreuen, die man
immer hier und da antrifft.
Um deswillen glaube ich verdienen folgende Beobachtungen als
Beiträge zu den bisherigen,
aber besonders von m.Cassini und Maraldi angestellten
Beobachtungen des Jupiters alle
Aufmerksamkeit.
I
Als ich am 26ten Oct. 1785 um 8St. 25´11´` wahrer bey sehr
reiner Luft mit 150. mahliger
Vergrr. meines 4 füßigen Herschelischen Telescops den Austritt
[p.2:] des 1ten
Jupiter-Monds [Io] beobachtete, sah ich zum ersten Male mit
völliger Deutlichkeit zwey
dunkle schwarze dicht neben einander in der Jupiters-Scheibe
befindliche Flecke, davon der
östlichste noch etwa noch einmal so groß als der andere war,
und an der Größe fast dem
Schatten des ersten Trabanten glich; dessen Durchmesser ich
mithin ohnegefähr auf 1,5”
schätze.
Beide Flecken waren nach Fig. 1 [lost] etwa 7/12 des Jupiters vom
westlichen Jupiters-Rande
entfernt, dicht nördlich über den mittelsten der zeither
beobachteten Streiffen befindlich,
und schienen mir damals in ihrer Bewegung nach Westen die von
Cassini bestimmte
Umdrehungs-Zeit zu befolgen. Um 10 U., da die Atmosphäre noch
ziemlich rein war, fand ich
jedoch überall keine Spur mehr davon.
In Ermangelung eines für diese nicht vorher vermuthete
Beobachtung schicklichen
Micrometers, war ich nicht vermögend, das Zeitverhältnis ihrer
Fortrückung genau zu
bestimmen und behielt solches den folgenden Tagen vor. Wegen
darauf erfolgter trüber
Witterung aber konnte cih erst am 29ten Oct. um 7St45´den
Jupiter wieder beobachten, da
nach der Cassinischen Umdrehungszeit diese Flecken gegen den
westlichen Rand des Jupiters
hätten sichtbar seyn müssen, fand sie jedoch nicht wieder.
Ebenso sah ich auch nachher am
3.5. und 6ten [?] zu den Zeiten, da diese Flecken wieder mitten
[p.3:] auf der
Jupiters-Scheibe sichtbar seyn mußten, auch nachher, überall
nicht wieder.
Gnug sie waren wirklich auf einmal wieder verschwunden und es
schien mir damals blos
auffallend zu seyn, daß ich unter den von Cassini und Maraldi
beobachteten Flecken noch
keinen gefunden, welcher mit der Rotation von 9 St 56´eine so
kurze Dauer gehabt hätte.
II
Am 15ten Nov. um 5St. 14´mitl Z., da ich hiernächst den
Schatten beobachten wollte den der
2te Trabant um solche Zeit auf die Jupiters-Scheibe werfen
mußte, erstaunte ich als ich
zwey verschiedene gleich große runde schwarze Schatten-Flecke
entdeckte, wovon nach Fig.2
der mitten auf der Scheibe in dem ssüdlichsten der damaligen 3
Streiffen der andere aber
etwas und zwar etwa um ¼ des Jupiters-Durchmesser mehr westlich
am mittelsten Streif,
mithin nur ein wenig nördlicher befindlich war, als wo nach der
damaligen Lage der 1te
Trabant in der unteren Conjunction vor der Scheibe vorüber ging.
Da beide Flecken sich durch ihre ganz schwarze Farbe und runde
Gestalt gleich stark
auszeichneten; so war mir solches eben so unerwartet, als es dem
Hern Maraldi war, da er am
26ten März 1707 einen [p4:] gleichen ungewöhnlichen schwarzen
Fleck des vor der Scheibe
damals befindlichen 4ten trabanten hielt und nur der
Einfallswinkel der Sonnenstrahlen
konnte mir zur Bestimmung dienen, welcher von beiden Flecken der
Schatten vom 2ten
Trabanten war.
Beide Flecken rückten gegen Westen fort und konnte ich, da
meiner Überraschung schon beide
die Mitte der Scheibe passiret waren, auch die Luft etwas
unreiner wurde, ihre
verhältnismäßige Bewegung nicht bestimmen.
Die übrigen 3.Trabanten-Schatten aber standen sämtlich an der
östlichen Seite und könnte
der ganz sonderbare, dem Trabanten Schatten ähnliche Fleck von
einem derselben nicht
entstehen.
Am 16. Nov. fiel trübeWitterung ein, welche abwechselnd
fortdauerte, und mich an der
weitern Beobachtung hinderte.
III
Am 21ten Nov[ember] um 7 St. mittlerer Zeit beobachtete ich
solchemnächst zwey ähnliche,
wie wol etwas kleinere runde schwarze Schattenpunkte, welche
gleich groß waren und nach
Fig. 3 beide dicht nordwärts am mittelsten Streif gegegn
den westlichen Rand sich
fortbewegten, auch dem Schatten eines Trabanten ähnlich waren;
welche aber sämtlich ihrer
damaligen lage und Entfernung nach nicht Ursach davon seyn
konnten.
[p 5:] Auch kommte nach der Cassinischen Rotation keiner von
beiden der am 15ten Nov.
beobachtete Fleck seyn. Ihr Abstand west- und östlich von von
einander betrug nicht völlig
ein drittheil des Jupiters-Durchmesser. Wegen entstehenden Windes
mußte ich die Beobachtung
aufgeben. ...” [9]
A long constant period of cloudy weather forced SCHROETER to
pause with his observations
till the 18th January 1786. At this day he noticed:
"Ich urtheilte, daß vielleicht aus diesem [p.6:] grauen
Fleck ein ganzer Streif entstehen
würde und scheine mich nicht geirrt zu haben ; denn nach lang
anhaltendenem trüben Wetter
bemerkte ich endlich am 18ten jan. d.J. um 6 U., daß genau in
derselben Lage und Richtung
ein neuer vierter ganz schmaler neblicher Streifen sich durch die
ganze sichtbare Halbkugel
des Jupiter sich verbreitete, den ich denn auch in der Folge bis
dahin, da der Jupiter
seinen Conjunktion sich näherte, als einen nicht die ganze Kugel
umschliessenden Streif,
von Zeit zu Zeit beobachtet habe.”
During the next cloudy period (18th Jan till 9th Feb) Schroeter
was able to construct a
Micrometer (Type “Herschelsches Lampen-Micrometer”). So
he could take empirical data’s on
his Observations at the 7th , 11th, 13th, 15th, 17th and 20th of
February . He made his
last reported Observation at the 21 and 25th of February. In
comparison between his
Observations from the 11 th and 13th SCHROETER noticed:
"Zugleich ergab sich aus dieser Vergleichung, daß dieser
kleine Fleck in einem ungefähr
gleichen Zeitverhältnis 25 Minuten früher in jede Linie kam als
der große Fleck vom 11.
Februar hätte kommen müssen, wenn er die Cassinische
Rotationsperiode befolgt hätte. Ein so
großer Irrtum schien mir aber unmöglich. Sollte er jedoch
wirklich eine sonderbare eigene
geschwindere von der nach Cassini bisher angenommenen der
Jupiters-Kugel nicht abhängige
Bewegung haben, dann bliebe nur die Möglichkeit, daß Cassini
sich sehr geirrt habe. Was ich
mir jedoch von einem so großen erfahrenen Beobachter absolut
nicht denken kann.”
This remark shows us the exactness of SCHROETERs observations. In
the 48 hours between the
11st and 13th of February Jupiter was turning 5 times . The
investigated difference of 25
minutes for 5 periods follows 5 minutes per period in difference
of the rotation between
the equatorial region and the higher latitudes. This difference
is comparable to
contemporary data. Schroeter was also able to differentiated
between the “short timed
blackish spots” and shadows of the Jupiter moons:
"Am 17. Februar, als die Jupiter-Scheibe so rein war, daß
ich um 7 Uhr 37´den halben
Schatten des dritten Trabanten [Ganymed] als eine ganz kleine
schwarzdunkle Halbkugel am
östlichen Rande in die Scheibe einrücken sah, war außer den
beiden Streifen weder etwas
Gekörntes noch etwas Gedrängtes darin zu sehen”
The similarity of the observations made by SCHROETER 1785/1786
and the optical observations
at the SL9-Impact 1994 should lead to a critical revaluation of
the SCHROETER manuscript.
Editorial Note: all notices in [brackets are made by the author.]
Cursiv printed words are
indicating a accentuation by SCHROETER.
Ref.:
[1] Schroeter, J. H. (1786): Manuscript University Library
Göttingen (MS Lichtenberg IV, 15)
[2] Schroeter, J.H. (1786b): Letter to Lichtenberg 18.Jun.1786
[1451]
[3] Schroeter J.H. (1786c) : Letter to Lichtenberg 31. Jul. 1786
[1466]
[4] Schroeter J.H. (1787): Observations sur la physique, sur l´
histoire naturelle et sur les arts 30, 117-124.
[5] Schroeter J.H. (1786d): Astr. Jahrb. für 1789, 180-191.
[6] Gumbert, H.L (1982): Bibliotheca Lichtenbergiana, 69.
[7] Gresky, W. (1974). Mitt. Gauss Ges. 17, 34
[8] Gerdes, D. (1986): Typoscript
[9] Gerdes, D [Ed.] (1993): Lichtenberg-Jahrbuch für 1992, 147-
160.
================
(4) FIRST IMAGES OF A COMET WITH ADAPTIVE OPTICS
O. Marco*), T. Encrenaz, E. Gendron: First images of a comet with
adaptive optics.
PLANETARY AND SPACE SCIENCE, 1998, Vol.46, No.5, p.547
*) PARIS OBSERVATORY, F-92190 MEUDON, FRANCE
Using the ADONIS adaptive optics system at ESO (La Silla, Chile),
on 8 March 1996, we made
the very first observation of a comet with adaptive optics. Comet
C/1996 B2 (Hyakutake) has
been imaged in the near-infrared (J, H, K bands at 1.2, 1.6 &
2.2 mu m respectively). The
achieved spatial resolution of approximate to 0.2 '', has allowed
us to isolate two
distinct dust-colour regions in the immediate neighbourhood of
the cometary nucleus. On a
[J-H] colour index map, a bluer region has been detected in the
sunward-facing hemisphere,
while a redder one is located symmetrically in the anti-solar
direction. The major dust
component in the coma remains silicates. These new observations
should help to constrain
the current models for dust components in comets. They clearly
demonstrate the feasibility
of observing comets with adaptive optics systems. Future
observations of comet Hale-Bopp
should greatly benefit from this new technique. (C) 1998 Elsevier
Science Ltd. All rights
reserved.
===============
(5) L-APLPHA OBSERVATIONS OF COMET HYAKUTAKE
J.L. Bertaux, J. Costa, E. Quemerais, R. Lallement, M. Berthe, E.
Kyrola, W. Schmidt, T.
Summanen, T. Makinen, C. Goukenleuque: Lyman-alpha observations
of comet Hyakutake with
SWAN on SOHO. PLANETARY AND SPACE SCIENCE, 1998, Vol.46, No.5,
pp.555-568
*) CNRS, SERV AERON, BP 3, F-91371 VERRIERES BUISSON, FRANCE
The SWAN instrument on board SOHO isa Lyman-alpha (L alpha)
photometer able to map the sky
intensity with a resolution of 1 degrees, and a capability of
microstepping (0.1 degrees).
SWAN is primarily devoted to the study of the large scale
distribution of solar wind from
its imprints on the interplanetary sky background, but was in
addition extensively
used to map the L alpha emission of several comets since its
launch in December 1995. Here
we report observations of comet C/1996 B2 (Hyakutake). Its L
alpha emission cloud extended
over more than 60 degrees while approaching the Earth at 0.102
AU. A comparison with a
simple model allowed hydrogen and H2O production rates to be
derived, while the comet
approached closer to the Sun from 1.12 AU to 0.53 AU distance to
the Sun, pre-perihelion.
The derived H2O production rate was found in fair agreement with
other derivations (IUE and
ground-based in the IR and UV), validating the L alpha method.
The H2O production by SWAN
was related to several other measurements of minor constituents
in order to derive new
values of abundance of CO, HCN, H2CO, CH3OH and CH3CN. Most
important, the D/H ratio in
comet Hyakutake is now found at 3 x 10(-4), as in comet Halley,
while a previous estimate
based on a wrong H2O number had indicated a value twice lower,
with important cosmogonic
consequences. The time evolution showed a fast surge on 21 March,
coinciding with the time
of fragmentation of the nucleus as detected 3 days later at Pic
du Midi. This surge is also
confirmed by the detailed comparison of H column densities
(observed vs model) as a
function of the distance to the nucleus, showing a larger ratio
in the inner region
(younger atoms) than in the outer region (older atoms) on 21
March, and then a progressive
filling-in of the H envelope. After the surge, there was a
plateau for 16 days around 1.8 x
10(29) H2O mol s(-1),and then an increase following approximately
a R-2 law. This behavior
is interpreted as the surge and plateau corresponding to the
fragmentation and total
disruption/evaporation of a fragment of the nucleus, of
approximately 200 m. Finally, it is
argued that the first detection of ethane C2H6 in this comet (IR
observations) might have
been the result of the special circumstances (a large fragment
disrupted very near the
Earth) rather than revealing a new special class of ethane-rich
comets as argued by other
authors. (C) 1998 Elsevier Science Ltd. All rights reserved.
==============
(6) MORE OBSERVATIONS OF COMET HYAKUTAKE
E. Gerard*), J. Crovisier, P. Colom, N. Biver, D. BockeleeMorvan,
H. Rauer: Observations of
the OH radical in comet C/1996 B2 (Hyakutake) with the Nancay
radio telescope. PLANETARY
AND SPACE SCIENCE, 1998, Vol.46, No.5, pp.569-577
*) MEUDON OBSERVATORY, ARPEGES, 5 PL J JANSSEN, F-92195 MEUDON,
FRANCE
The 18-cm lines of the OH radical were monitored in C/1996 B2
(Hyakutake) with the Nancay
radio telescope between 1 March and 18 May 1996. Besides
providing regular measurements of
the water production rate, the C/1996 B2 campaign was useful to
test and improve existing
models of the OH density; excitation and transfer because the
comet passed successively
close to the Earth and close to the Sun. At the time of closest
approach to Earth, a rough
mapping was made by observing at offset positions several
beam-widths (3.5') from the
nucleus together with the centre :, position. The OH line
intensity at the centre was
comparable to those at offset positions, providing direct
evidence for collisional
quenching of the OH maser in the inner coma. After removing the
Greenstein effect, The line
profiles suggest a slight excess outgassing towards the Sun. We
are able to detect the OH
satellite lines at 1612 and 1721 MHz. A weak Zeeman splitting of
the 1667 and 1665 MHz
transitions was observed :corresponding to an average
line-of-sight magnetic field in the
range +5 to +10 nT. (C) 1998 Elsevier Science Ltd. All rights
reserved.
===============
(7) CHECHING MOLUCULES ON COMET HYAKUTAKE
J.G.A. Wouterloot*), A. Lingmann, M. Miller, B. Vowinkel, G.
Winnewisser, F. Wyrowski: HCN,
CO, CS, CN, and CO+ observations of comet Hyakutake (1996 B2).
PLANETARY AND SPACE SCIENCE,
1998, Vol.46, No.5, pp.579-584
*) UNIVERSITY OF COLOGNE, INST PHYS 1, ZULPICHER STR 77, D-50937
COLOGNE, GERMANY
In March and April 1996 we observed the comet Hyakutake (1996 B2)
with the KOSMA 3-m
telescope. We detected the J = 2-1 and 3-2 transitions of CO, and
the J = 3-2 and 4-3
transitions of HCN on several days during this period. In
addition we detected CS J = 7-6
on one occasion. We observed, but did not detect, several
transitions of CN (N = 2-1 and N
= 3-2), and CO+ N = 3- 2. From our results we derive production
rates of the different
molecules or upper limits. The simultaneous observations of
different transitions and
different molecules allow a comparison of those rates and of the
assumed excitation model.
The KCN spectra show variability by about 50% on a time scale of
hours. (C)1998 Published
by Elsevier Science Ltd. All rights reserved.
==================
(8) CONDENSATIONS OF C2 in COMET HYAKUTAKE
C. Laffont*), P. Rousselot, J. Clairemidi, G. Moreels:
Condensations and diffuse source of
C-2 in comet Hyakutake C/1996 B2. PLANETARY AND SPACE SCIENCE,
1998, Vol.46, No.5,
pp.585-601
*) BESANCON OBSERVATORY, BP 1615, F-25010 BESANCON, FRANCE
An observation program of Comet Hyakutake C/1996 B2 was
conducted in the long-slit
spectrometric and narrow-band imagery modes at the Observatoire
de Haute Provence on March
24-25 and March 30-April 2, 1996. Images in the continuum taken
on March 31, at 19 h 30 UT,
show dust jets in the solar-side hemisphere and the presence of
two condensations at r =
2000 and 8000 km (+/-200 km) along a line in the anti-solar
direction. Images in the C-2
(1, 1) (at 513 nm) and (0, 0) (at 516 nm) bands show the presence
of an are perpendicular
to the anti-solar direction at r = 2000 km(+/- 200 km). A
bi-dimensional visualisation of
the 513 nm/516 nm intensity ratio for C-2 and of the dust ''red''
colour parameter given by
the 682 nm/527 nm intensity ratio shows that both parameters are
correlated in the inner
coma at r < 5000 km. Synthetic spectra of C-2 are calculated
by using a model in which the
vibrational and rotational temperatures are adjusted in order to
obtain the best fit to the
measured spectra. It is shown that both temperatures increase
with increasing cometocentric
distance. The C-2 513 nm/516 nm ratio shows a V-type behaviour
centred on the nucleus, with
the exception of a region around 1200 km where it reaches a
maximum value. It is suggested
that the condensations are dust particle clusters released by the
nucleus, which create a
diffuse source producing the C-2 molecules at a high excitation
temperature. The colour of
dust in this scheme suggests that the diffuse source contains a
higher proportion of small
grains than the surrounding coma. (C) 1998 Elsevier Science Ltd.
All rights reserved.
=====================
(9) X-RAYS FROM COMETS
R. Wegmann*), H.U. Schmidt, C.M. Lisse, K. Dennerl, J.
Englhauser: X-rays from comets
generated by energetic solar wind particles. PLANETARY AND SPACE
SCIENCE, 1998, Vol.46,
No.5, pp.603-612
*) MAX PLANCK INSTITUTE OF ASTROPHYSICS, D-85748 GARCHING,
GERMANY
By means of axisymmetric hydrodynamic models with chemistry we
study the X-ray emission of
two processes in a comet: Bremsstrahlung of solar wind electrons
interacting with the
neutral gas coma, and :charge exchange of heavy solar wind ions
in high ionization states
with the neutral cometary gas. Comparisons of morphology,
intensity and spectrum with
observations favour heavy ions as the emitting agent (C) 1998
Elsevier Science Ltd. All
rights reserved.
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