Universität zu Köln

Paetzold, Martin, Andert, Tom, Jacobson, Robert, Rosenblatt, Pascal and Dehant, Veronique (2014). Phobos: Observed bulk properties. Planet Space Sci., 102. S. 86 - 95. OXFORD: PERGAMON-ELSEVIER SCIENCE LTD. ISSN 0032-0633

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Abstract

This work is a review of the mass determinations of the Mars moon Phobos by spacecraft close flybys, by solving for the Martian gravity field and by the analysis of secular orbit perturbations. The absolute value and accuracy is sensitive on the knowledge and accuracy of the Phobos ephemeris, of the spacecraft orbit, other perturbing forces acting on the spacecraft and the resolution of the Martian gravity field besides the measurement accuracy of the radio tracking data. The mass value and its error improved from spacecraft mission to mission or from the modern analysis of old tracking data but these solutions depend on the accuracy of the ephemeris at the time of observation. The mass value seems to settle within the range of GM(Ph)=(7.11 +/- 0.09) x 10(-4) km(3) s(-2) which covers almost all mass values from close flybys and distant encounters within its 3-sigma error (1.5%). Using the volume value determined from MEX HRSC imaging, the bulk density is (1873 +/- 31) kg m(-3) (3-sigma error or 1.7%), a low value which suggests that Phobos is either highly porous, is composed partially of light material or both. The determination of the gravity coefficients C-20 and C-22 from the Mars Express 2010 close flyby does not allow to draw conclusion on the internal structure. The large errors do not distinguish whether Phobos is homogeneous or not. In view of theories of the Phobos' origin, one possibility is that Phobos is not a captured asteroid but accreted from a debris disk in Mars orbit as a second generation solar system object. (C) 2014 Elsevier Ltd. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Paetzold, Martin UNSPECIFIED UNSPECIFIED UNSPECIFIED Andert, Tom UNSPECIFIED UNSPECIFIED UNSPECIFIED Jacobson, Robert UNSPECIFIED UNSPECIFIED UNSPECIFIED Rosenblatt, Pascal UNSPECIFIED UNSPECIFIED UNSPECIFIED Dehant, Veronique UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-424855
DOI:	10.1016/j.pss.2014.01.004
Journal or Publication Title:	Planet Space Sci.
Volume:	102
Page Range:	S. 86 - 95
Date:	2014
Publisher:	PERGAMON-ELSEVIER SCIENCE LTD
Place of Publication:	OXFORD
ISSN:	0032-0633
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ASTEROID 21 LUTETIA; MASS DETERMINATION; MARS EXPRESS; GRAVITY; ORBITS; FLYBY; FIELD Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/42485