  In this paper we present a mission architecture and a robotic platform, the
Shapeshifter, that allow multi-domain and redundant mobility on Saturn's moon
Titan, and potentially other bodies with atmospheres. The Shapeshifter is a
collection of simple and affordable robotic units, called Cobots, comparable to
personal palm-size quadcopters. By attaching and detaching with each other,
multiple Cobots can shape-shift into novel structures, capable of (a) rolling
on the surface, to increase the traverse range, (b) flying in a flight array
formation, and (c) swimming on or under liquid. A ground station complements
the robotic platform, hosting science instrumentation and providing power to
recharge the batteries of the Cobots. In the first part of this paper we
experimentally show the flying, docking and rolling capabilities of a
Shapeshifter constituted by two Cobots, presenting ad-hoc control algorithms.
We additionally evaluate the energy-efficiency of the rolling-based mobility
strategy by deriving an analytic model of the power consumption and by
integrating it in a high-fidelity simulation environment. In the second part we
tailor our mission architecture to the exploration of Titan. We show that the
properties of the Shapeshifter allow the exploration of the possible
cryovolcano Sotra Patera, Titan's Mare and canyons.
