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Current sheets (CSs) play a crucial role in the storage and conversion of magnetic energy in planetary magnetotails. Using high-resolution magnetic field data from MAVEN spacecraft, we report the existence of super thin current sheets (STCSs) in the Martian magnetotail. The typical half-thickness of the STCSs is similar to 5 km, and it is much less than the gyroradius of thermal protons (rho(p)). The STCSs are embedded into a thicker sheet with L >= rho(p) forming a multiscale current configuration. The formation of STCS does not depend on ion composition, but it is controlled by the small value of the normal component of the magnetic field at the neutral plane (B-N). A number of the observed multiscale CSs are located in the parametric map close to the tearing-unstable domain, and thus, the inner STCS can provide an additional free energy to excite ion tearing mode in the Martian magnetotail.

Plain Language Summary We investigate the structure of cross-tail current sheets (CSs) in the Martian magnetotail. The CSs play a crucial role in the conversion of magnetic energy into kinetic and thermal energy of plasma particles via magnetic reconnection. Signatures of magnetic reconnection were reported in the Martian magnetotail, but the mechanisms leading to reconnection onset are still unknown. Previous observations in the Earth magnetotail showed that the stretching of the CS magnetic configuration leads to formation of thin CS embedded into a thicker one. Such multiscale configuration can be a source of free energy for excitation of ion tearing mode. The development of this mode can generate X-type and/or O-type magnetic configuration and trigger reconnection. By using MAVEN spacecraft observations, we reported the formation of multiscale CS structure in the Martian magnetotail with the inner super thin current sheet (STCS) having a half-thickness much less than proton gyroradius. We showed that the STCS can be in the metastable state. Thus, the CS thinning and the formation of STCS can lead to a new metastable equilibrium, in which the CS undergoes topological changes enabling the process of fast magnetic reconnection.