"We present a mission architecture to address both high-priority science identified for Marsʼ moons and strategic knowledge gaps for the future Human exploration in the Martian system. The basic architecture involves a mother spacecraft and one or several minimalistic in-situ mobility platforms, called spacecraft/rover hybrids, first studied under the 2011 NASA Innovative Advanced Concepts (NIAC) program.
The mission aims at exploring the surface of Phobos in proximity to the Stickney crater. This region is of particular interest for several reasons. First, previous missions have identified spectral similarities between some terrains in the Stickney region and C-type asteroids, i.e., asteroids that are believed to be rich in water and organics and related to carbonaceous chondrites. Besides, this area displays a large complexity in terms of terrain properties, variations in regolith color, mass wasting, ejected blocks, etc., which makes it a particularly interesting exploration target.
In order to explore these different terrains, one needs a mobility platform that can both achieve a spatial coverage of a few kms and access discrete and narrow areas through fine mobility. This is particularly difficult due to the very low gravity environment, which challenges traditional forms of mobility such as wheeled or legged platforms. In our mission architecture, this capability would be provided by the aforementioned hybrids, which are minimalistic platforms employing an innovative mobility mechanism and carrying a suite of instruments complementing those on the mother spacecraft (which would act as a communication relay to Earth and perform remote measurements). Specifically, a spacecraft/rover hybrid is a multi-faceted geometric solid that encloses three mutually orthogonal flywheels and is surrounded by external spikes. The combination of the actuation of the flywheels with the enclosureʼs and spikes' geometry would enable controlled tumbles (for fine mobility) and hops (for large surface coverage). This mobility concept has been validated on a number of microgravity test beds at JPL and Stanford, and has been recently selected for further validation on NASA’s parabolic aircraft flights.
The current state of miniaturized instrumentation allows the accommodation of several geophysical instruments and one analytical instrument within the hybrids, which, in conjunction with a stereo camera and a dust analyzer on the mothership, could provide key information about the physical properties and composition of the surface. Accordingly, a fundamental aspect of this architecture is that the responsibility for primary science would be shared between the mothership and the hybrids. The mothership would provide broad area coverage, while the hybrids would zoom in on specific areas and conduct in-situ measurements."