The Tumbleweed Mission: A new paradigm of Martian exploration through swarm-based, wind-driven rovers

Comprehensive characterisation of Mars requires global surface observations at high resolution. However, current exploration is conducted through large, infrequent, risky, and relatively high-cost space missions that gather highly localised data. For human missions in the upcoming decades, a new paradigm of exploration involving notable reductions in cost, risk, and timeframe is necessary.

The Tumbleweed Mission proposes a novel architecture, with a swarm of 90 spheroidal, autonomous, wind-driven, and solar-powered mobile impactors (rovers). Unfolding mid-air, they land near one of the poles and spread across the Martian surface for approximately 90 sols. Each impactor follows a different route, planned with consideration for the topography, wind conditions and sites of scientific interest. Once the desired spatial distribution is achieved, the rovers are arrested to a stationary phase for an undefined period. Rovers collect scientific data during both mobile and stationary phases. Each 5-meter diameter, 20 kg rover accommodates up to 5 kg of scientific payload.

The mission aims to produce (atmospheric) data over a multitude of spatial and temporal scales, corresponding to existing strategic knowledge gaps as outlined by NASA’s Mars Exploration Program Analysis Group (MEPAG). The mission would be able to characterise the dynamical and thermal state of the lower atmosphere and controlling processes on local to regional scales. Measure variations in the abundance of species such as water vapour, carbon dioxide and methane. As well as improve constraints to computational models and overall understanding of Martian climate and weather. In the stationary phase, Environmental Sensing Suites (ESS) will act as weather stations, providing frequent near-surface atmospheric data from up to 90 surface points of Mars to allow for the observation of changes at hourly, diurnal and seasonal time scales. Additionally, the ionising radiation environment at the surface would be characterised by unprecedented spatio-temporal resolution. The geomorphology and composition of previously inaccessible areas of Mars can now be constrained through imaging and spectroscopy. Also, the large network setup could provide Martian mantle properties through continuous measurements of nutation, precession, tidal deformation, and gravimetry. Identifying the abundance of carbon and other biologically important (CHNOPS) elements near the surface would provide contextual information concerning habitability and possibly, evidence of indigenous life. Surface measurements can be used to map future landing sites to mitigate the risks posed by hazardous terrain and radiation exposure.

The rover swarm will leverage a heterogeneous complement of analytical instruments during the mission and mostly employ legacy instruments. Currently, the integrated set of instrumentation is under investigation through an objective trade-off. A preliminary list includes a multispectral camera, environmental sensing suite, magnetometer, radio beacon, laser retroreflector, and miniaturised spectrometers. The next stage of development involves testing the proposed instrumentation in Mars analogous environments.

By providing large-scale data sets using rover swarms, the Tumbleweed Mission offers the opportunity to make deep space accessible for everyone. The presentation will provide an overview of the mission concept, review the most desirable science applications and their relevance to MEPAG goals, and discuss the instrument recommendations and main limitations.