The Measurements of The Phobos Magnetic Field During The Phobos-2 Mission

The measurements obtained by the magnetometers during the Phobos-2 mission from March 22 to March 26, 1989, are discussed. In particular it is suggested that the solar wind interaction with Phobos and the rotating direction of the magnetic field in the circular orbits around Mars are the evidence for the existence of an intrinsic plane- tary field of Phobos with a dipole moment of the order of 10^18 Gauss cm^3 . The discovery of the Phobos magnetic field was studied in [1,2]. The magnetization of the Phobos substance is 0.15 CGS. It should be noted that there are some meteorites with a magnetization of 3 CGS [3]. Phobos is the magnetized body, rotating around Mars so; it always presents the same face to a hypothetical observer on Mars. The peculiarity of the rotation of the magnetized Phobos supplies the magnetic field signatures, which, specifically the direction, are phase locked with Phobos rotation rate. To resolve this issue completely, in situ measurements from Phobos vicinity are required. The Pho- bos space project had had a very complicated scheme of flight relative to Phobos and the organization of a unique experiment named "Celestial Mechanics". The spacecraft was inserted into such an orbit around Mars on 22 March 1989 that it remained perma- nently within the vicinity of Phobos until 27 March. The direct experimental evidence of the Phobos magnetic field was obtained from the observations during the Phobos mission.

Reference: [1] Mordovskaya, V.G., V.N. Oraevsky, and J. Rustenbach, The Phobos interaction with the solar wind plasma, Cosmic Research, vol. 39, iss. 5, 2001. [2] Mordovskaya, V.G., V.N. Oraevsky, V.A. Styashkin, and J. Rustenbach, Experimental evidence of the Phobos magnetic field, JETP Letters, vol. 74, iss. 6, pp. 293-297, 2001. [3] Gus'kova, E.G., Magnetic properties of meteorites, M.: Nayka, 1972.