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IAUC 7660: P/2001 MD_7; MARS

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                                                  Circular No. 7660
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


COMET P/2001 MD_7 (LINEAR)
     M. Blythe, Lincoln Laboratory Experimental Test System,
reports the discovery by LINEAR of a comet on images obtained on
July 11, when it appeared diffuse.  Subsequent observations
permitted identification with the object 2001 MD_7, so designated
on MPS 31852 as a result of LINEAR observations made on June 21 and
24.  L. Sarounova reports that CCD images of the comet obtained on
July 12.9 UT at Ondrejov show a bright nucleus and faint coma.

     2001 UT             R.A. (2000) Decl.        m2
     June 21.30593   19 12 54.22   -10 23 10.6   17.6
     July 11.21836   18 53 34.78   -12 20 04.6

     Full astrometry is given on MPEC 2001-N27, as are the
following orbital elements by B. G. Marsden (from 38 observations,
June 21-July 12):

     T = 2001 Nov. 30.4679 TT         Peri. = 244.4228
     e = 0.670640                     Node  = 129.3848  2000.0
     q = 1.261944 AU                  Incl. =  13.3635
       a =  3.831499 AU    n = 0.1314168    P =   7.500 years


MARS
     V. A. Krasnopolsky, Catholic University of America; and P. D.
Feldman, Johns Hopkins University, write:  "We obtained a spectrum
(range 90-119 nm; spectral resolution 0.02 nm) of Mars on May 12
using the Far Ultraviolet Spectroscopic Explorer.  Among other
emissions, the spectrum reveals weak H_2 lines of the Lyman-band
system at 107.162, 111.861, and 116.676 nm.  All of these lines
originate from the v' = 6, J' = 0 level that is excited by the
solar Lyman-beta photons.  The detected lines are the first
observational evidence for molecular hydrogen on Mars.  Detection
of H_2 on Mars was impossible for the numerous spacecraft that
visited Mars; an attempt to detect H_2 by averaging the Mariner 9
ultraviolet spectra resulted in an upper limit of 1.5 rayleighs for
the H_2 emission at 160.75 nm (Moos 1974, J. Geophys. Res. 79,
2887).  H_2 is a product of water-vapor chemistry on Mars, and the
observed lines correspond to an H_2 mixing ratio of approximately
20 parts per million in the lower atmosphere."

                      (C) Copyright 2001 CBAT
2001 July 12                   (7660)            Daniel W. E. Green

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