Mars' plasma system. Scientific potential of coordinated multipoint missions: "The next generation"

Abstract

The objective of this White Paper, submitted to ESA's Voyage 2050 call, is to get a more holistic knowledge of the dynamics of the Martian plasma system, from its surface up to the undisturbed solar wind outside of the induced magnetosphere. This can only be achieved with coordinated multi-point observations with high temporal resolution as they have the scientific potential to track the whole dynamics of the system (from small to large scales), and they constitute the next generation of the exploration of Mars analogous to what happened at Earth a few decades ago. This White Paper discusses the key science questions that are still open at Mars and how they could be addressed with coordinated multipoint missions. The main science questions are: (i) How does solar wind driving impact the dynamics of the magnetosphere and ionosphere? (ii) What is the structure and nature of the tail of Mars' magnetosphere at all scales? (iii) How does the lower atmosphere couple to the upper atmosphere? (iv) Why should we have a permanent in-situ Space Weather monitor at Mars? Each science question is devoted to a specific plasma region, and includes several specific scientific objectives to study in the coming decades. In addition, two mission concepts are also proposed based on coordinated multi-point science from a constellation of orbiting and ground-based platforms, which focus on understanding and solving the current science gaps.

Keywords: Coordinated multipoint missions; ESA-Voyage2050; Future missions; Mars; Plasma; Science gaps.

Fig. 1

Schematic of Mars’ plasma system showing the main physical processes known to occur at Mars. The Sun is to the left. Multi-point plasma measurements are needed to understand the whole dynamic system at Mars. (Picture adapted from Lillis et al. [81], and from Fran Bagenal and Steve Bartlett (CU-LASP))

Fig. 2

Global time-dependent MHD simulation of the Mars-solar wind interaction under quiescent solar wind conditions but allowing the crustal magnetic fields to continuously rotate with time. Top panels: at 8:00 UT. Bottom panel: at 21:00 UT

Fig. 3

Figure from Matta et al. [92]. Model results of (a) electron and (b) ion temperature profiles with additional topsideheating flux compared with Viking Lander 1 temperatures (dotted black lines)

Fig. 4

Orbit configuration (in Mars-Solar-Orbital cylindrical coordinates) of the different missions that have transited the Martian tail with specific plasma instrumentation. The orbits correspond to their furthest transit within the Martian tail. As observed, the tail from ~3.5-4 Mars radii has not been much explored, with the exception of the Rosetta and Mars-4 and 5 single flybys of Mars. We note Phobos-2 and Mars-4 and 5 are not included in this Figure but are discussed. The Sun is to the left. BS and MPB stand for bow shock and magnetic piled-up boundary, respectively. Phobos and Deimos orbits are plotted for context

Fig. 5

Typical dayside (left) and nightside (right) Martian ionospheric profiles. The different atmospheric layers, and main internal and external forcings: solar radiation, meteors, electron and solar storm particle precipitation, solar wind, magnetic fields, gravity waves, dust storms, and atmospheric cycles are also indicated

Fig. 6

Dayside electron density measured with the Mars Express Radio Science experiment (MaRS). Black and gray circles show the electron density derived from X-band and differential Doppler. The black straight line is the zero line, the dashed black and gray lines indicate the associated noise levels, the black dash-dotted line is the lowest valid altitude of observation. (a) Day of Year (DoY) 350 (2005), SZA = 74.07°. (b) DoY 337 (2013), SZA = 57.16°. Radio science data courtesy of the MaRS-Mars Express team

Fig. 7

MAVEN plasma density profiles from orbit 6206. Simulations with photochemistry are shown as thin dotted profiles, and simulations with added transport are shown as thin solid profiles. This Figure highlights the large role that the neutral atmosphere has a driver for small plasma structure. Figure from Mayyasi et al. [95]

Fig. 8

Left: Mars’ electron density profile, including the M2 and M1 layers, and a transient lower layer M*, and schematics of the detection of this profile using orbital sounding (A), surface sounding (C), and (right) radio occultation (B)