  We study the structure of atomic hydrogen (HI) in the host galaxy of GRB
171205A / SN 2017iuk at z=0.037 through HI 21cm emission line observations with
the Karl G. Jansky Very Large Array. These observations reveal unusual
morphology and kinematics of the HI in this otherwise apparently normal galaxy.
High column density, cold HI is absent from an extended North-South region
passing by the optical centre of the galaxy, but instead is extended towards
the South, on both sides of the galaxy. Moreover, the HI kinematics do not show
a continuous change along the major axis of the galaxy as expected in a
classical rotating disk. We explore several scenarios to explain the HI
structure and kinematics in the galaxy: feedback from a central starburst
and/or an active galactic nucleus, ram pressure stripping, accretion, and tidal
interaction from a companion galaxy. All of these options are ruled out. The
most viable remaining explanation is the penetrating passage of a satellite
through the disk only a few Myr ago, redistributing the HI in the GRB host
without yet affecting its stellar distribution. It can also lead to the rapid
formation of peculiar stars due to a violent induced shock. The location of GRB
171205A in the vicinity of the distorted area suggests that its progenitor
star(s) originated in extreme conditions that share the same origin as the
peculiarities in HI. This could explain the atypical location of GRB 171205A in
its host galaxy.
