The state of Mars' present day atmosphere is integral to forming a complete understanding of its climate, including the possible emergence and evolution of biological life. Investigating atmospheric characteristics at various scales is essential for enabling an effective, holistic understanding of the Martian climate, surface environment and habitability. Additionally, the ionizing radiation environment is one of the main factors impacting surface habitability and atmospheric loss. Long-term exposure to ionizing radiation poses concerns for future human exploration. However, given the sparse and incomplete nature of present environmental datasets, creating sufficiently accurate, detailed and complete models of atmospheric processes and interactions is not feasible. Till now, most investigations of Mars' atmosphere have been limited to orbiters and solitary landers or rovers, which leaves a considerable gap in the ability to acquire datasets with satisfactory surface coverage and spatio-temporal resolution. This paper describes various aspects of a novel science & exploration mission equipped with payloads aimed at the acquisition of these much-needed datasets. The proposed Ultimate Tumbleweed Mission will consist of a swarm of wind-driven mobile impactors with the ability to morph into measurement stations, so as to explore the Martian surface and collect measurements of near-surface meteorological parameters. Following a brief description of the notional mission concept and spacecraft design, we describe the scientific value that can be returned during the mobile and stationary phases of said mission. Datasets from a networked set of Tumbleweed Measurement Stations would enable the refinement of Martian climate and weather models. Through various in-situ measurements, micro- and meso-scale atmospheric phenomena and processes involving interaction between water, dust, and carbon dioxide can be constrained and studied in order to fill existing knowledge gaps. The swarm would help in investigating the ionizing radiation environment on Mars by acquiring direct measurements of flux, absorbed dose, spectral distribution, and angular distribution of various high-energy particles and their secondaries. Atmospheric modulation of incident cosmic rays and solar energetic particles, the nature and abundance of secondary particles, exposures and hazards for electronic and biological systems, and the shielding properties of the Martian regolith as well as natural landscape can be understood further, in order to prepare for future human and robotic exploration missions to the Red Planet. Preliminary formulation of the science case - including a set of candidate instruments - indicates that a network of Tumbleweed Measurement Stations can deliver holistic in-situ characterization of various near-surface atmospheric phenomena as well as the ionizing radiation environment on Mars.

To date, in-situ Mars exploration has provided planetary scientists with a unique opportunity to understand the planet and the history of the solar system, as 45% of the Martian surface is comprised of geological units dated more than 3.7 billion years old. However, fundamental mechanisms of surface geological and geomorphological features on Mars cannot be determined by current missions, as they are limited by small surface coverage or limited resolution. As a result, there is a limited understanding of the presence of turbidite deposits along the Martian dichotomy, which would provide direct evidence of ancient deep-water environments. Additionally, the mechanisms of equatorial Recurring Slope Lineae (RSL) are debated along with glacier-like forms (GLFs) present in the polar regions of Mars. Studying them in-situ would enable further comprehension of the extent of surface liquid water, paleoclimates on Mars, and the possibility of future human habitation on Mars. The need for large-scale spatiotemporal datasets is addressed by a novel mission architecture that uses a swarm of wind-driven mobile impactors - the Tumbleweed Rovers. The Ultimate Tumbleweed Mission is able to provide high coverage and high-resolution imaging at rugged and previously inaccessible locations on Mars. The objective of this paper is to investigate the utility of a multispectral camera and a hand-lens style imager integrated into a swarm of Tumbleweed Rovers, in order to answer long-standing questions regarding the geologic history and modern geomorphology on Mars. We conduct a definitive feasibility study of the instrumentation on a swarm of Tumbleweed Rovers, defining design requirements to attain baseline science goals. The proposed multispectral camera is capable of distinguishing between the major mineral groups relevant to Mars, e.g. olivine, iron-oxides, and hydrated minerals. We also propose a hand-lens style imager, capable of determining the distribution of grain sizes present in common sedimentary formations (sandstones, siltstones, and mudstones). With this instrumentation, we show that the Ultimate Tumbleweed Mission (UTM) enables searching for turbidites, constraining the composition and mechanics of RSL, and mapping the extent of glacier-like forms in the high latitudes. In this paper, we demonstrate that Tumbleweed Rovers can significantly improve our understanding of the geology and modern geomorphology of Mars by providing high-resolution images at rugged, high-latitude locations.