Robert James Lillis

Small‐scale (10 s of km) currents in the Martian atmosphere may result in atmospheric heating, ionization, discrete aurora, and atmospheric escape. We have developed a semi‐automated method to identify current signatures in the Martian upper atmosphere using perturbations in the local magnetic field. We use magnetic field measurements taken by Mars Atmosphere and Volatile EvolutioN to investigate the incidence of ionospheric current signatures on the nightside of the planet in regions of moderate to strong crustal fields ( 25 nT). We find that current signatures are uncommon in horizontal magnetic fields but are detected up to 100% of the time in magnetic cusp regions, where the field is nearly radial. Current signatures are more common post‐dusk than predawn, which is consistent with auroral emission. Current signatures are most common in the ionospheric dynamo region, where ion motion is driven by the neutral atmosphere and electrons are bound to magnetic field lines. The occurrence of current signatures does not appear to be influenced by interplanetary magnetic field direction, solar wind dynamic pressure, or solar extreme ultraviolet photon flux.

The Martian ionosphere hosts complex current systems driven both by solar wind interactions and neutral wind dynamo processes. While the global patterns of these current systems have been statistically examined, their detailed structures and orientations remain poorly constrained. Using magnetic field observations from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft during the Deep Dip 2 campaign, we resolve the horizontal components of dayside ionospheric currents over regions without strong Crustal Magnetic Fields (CMF). The currents are most prominent between 130 and 150 km altitude, with peak magnitudes of ∼1 μA/m ² , and are oriented counterclockwise from, and roughly perpendicular to, the draped Interplanetary Magnetic Field in the horizontal plane when viewed from above. Theoretically calculated neutral wind‐driven dynamo currents show significant discrepancies from the derived currents, likely reflecting uncertainties in neutral winds and conductivities. In contrast, simulated magnetohydrodynamic (MHD) ionospheric currents, which are purely solar wind‐induced in the model, share similar features with the derived currents. We conclude that, for the four cases examined here, which were sampled in near‐subsolar regions with weak CMF, the derived ionospheric currents are more consistent with a solar wind‐induced origin, whereas neutral wind‐driven dynamo currents may play only a minor role under these conditions.

Observations of ultraviolet dayglow provide valuable insights into the composition, energetics, and dynamics of planetary atmospheres. The Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) uniquely captures extreme ultraviolet (EUV) and far ultraviolet (FUV) emissions from Mars’ upper atmosphere. Previous work reported irregular brightness enhancements referred to as “bright spots” in approximately one quarter of the OI1304 dayside disk images that are not linked to instrument noise or fluctuations in solar EUV flux. The origin of these enhancements is currently unknown. Here, we analyze a full Mars year of EMUS dayside disk observations to characterize the spectral, spatial, local time, and seasonal behavior of these bright spots. A clear preference for occurrence from early morning to afternoon local times is seen, with evidence of seasonal variability. Spectral analysis indicates that the cause of the bright spots is likely compositional and not auroral. These results provide evidence for intermittent, medium-scale compositional structure of unknown origin in the Martian thermosphere that is not explained by expected dayglow variations, providing new observational constraints for models.

By implementing an alternate regional mapping approach that selects MAVEN orbit passes with periapses below 170 km within the region of interest and directly compares magnetometer data along adjacent tracks, more accurate regional maps of the Mars crustal magnetic field are constructed. Results for the Claritas Fossae region south of Tharsis show a more detailed correlation than previously found in Mars Global Surveyor (MGS) data between magnetic anomalies and areas of ancient magmatic activity and uplift. These anomaly sources are interpreted to consist of magmatic intrusions magnetized thermoremanently in an oxidizing, hydrothermal environment during early Mars history when the planetary dynamo was still active. Similarly, mapped anomalies near Olympus Mons are consistent with thermal demagnetization in the absence of a dynamo during the Late Hesperian and Amazonian epochs when its final eruptions occurred. Weak anomalies over the Syrtis Major calderas and the Tyrrhenus Mons caldera further support partial thermal demagnetization of the underlying older terrain. Hadriacus Mons has previously been reported to have a magnetization signature based on MGS electron reflectometry data. The regional mapping reported here confirms that anomalies extend southwestward from the Hadriacus Mons central caldera toward Hellas, following the direction of apparent pyroclastic flow deposits with model ages ranging from 3.7 to 3.9 Ga. If future lower‐altitude measurements demonstrate that these anomalies are indeed associated with the asymmetric flanks of Hadriacus Mons, it would follow that dynamo activity continued into the Late Noachian or Early Hesperian epochs.

Magnetotail current sheet (CS) flapping is a universal plasma phenomenon observed at multiple planets, yet its triggering mechanisms remain poorly understood outside of Earth. At Mars, single‐spacecraft observations have also reported tail flapping, but the processes responsible for its onset have never been identified. In this study, we investigate the potential correlation between magnetic reconnection and magnetotail flapping using multipoint measurements from Mars Atmosphere and Volatile EvolutioN (MAVEN) and Tianwen‐1 (TW‐1) missions. We analyze an example event in which MAVEN observed a reconnection‐associated CS crossing in the near tail while TW‐1 simultaneously detected CS flapping further downtail. A statistical survey of joint observations from November 2021 to February 2024 identifies that about two‐thirds of TW‐1 flapping events coincide with reconnection signatures observed by MAVEN. Multiple magnetic flux ropes were also detected before or during flapping intervals, similar to previous observations at Earth, suggesting that reconnection‐generated magnetic flux ropes may propagate tailward and drive plasma instabilities that trigger the tail flapping at Mars. These results provide the first multipoint evidence of a potential statistical correlation between magnetic reconnection and magnetotail flapping at Mars, enabling us to explore the potential triggering mechanism of magnetotail flapping. Our findings also offer new insights into Martian magnetotail dynamics and broaden the comparative understanding of this fundamental plasma process across planetary environments.

On 9 October 2024, a major Solar Energetic Particle (SEP) event was detected simultaneously across a wide range of heliolongitudes and heliocentric distances. Signatures were observed by Solar Orbiter, Parker Solar Probe (PSP), STEREO-A, near-Earth spacecraft (SOHO, GOES, ACE), and surface instruments on Mars (MSL/RAD). The event originated from an X1.8 solar flare in Active Region (AR) 3848, which produced a fast, Earth-directed full-halo coronal mass ejection (CME). This study aims to characterize the acceleration and heliospheric distribution of SEPs during this event and to evaluate its implications for space weather forecasting and radiation risks for future human exploration of Mars. We combined imaging and in situ particle observations from multiple spacecraft positioned at different longitudes and heliocentric distances. Analyses included flare and CME timing, SEP fluxes, onset times, and energy spectra at each vantage point. Multi-point comparisons allowed us to assess how CME-driven shocks accelerate and transport SEPs, and how cross-field propagation and interplanetary scattering shaped the observed particle distributions, particularly at Mars.The X1.8 flare began at 01:25 UTC, peaked at 01:56 UTC, and ended at 02:43 UTC. The associated full-halo CME was first detected by LASCO at 02:12 UTC from ~N13 W08, with speeds estimated at ~1,500 km/s (leading edge) and ~2,100 km/s (shock front). The CME arrived at Earth around 10 October 14:45 UTC. Solar proton intensities began rising at 02:40 UTC and reached S2 (moderate) radiation storm levels by 07:30 UTC. Widespread SEP detections, including at Mars, demonstrate efficient particle acceleration over an exceptionally broad spatial domain and highlight the role of extended shock fronts, cross-field diffusion, and interplanetary turbulence in shaping SEP propagation. These results provide critical constraints for SEP transport models and underline the value of multi-point observations for advancing forecasting capabilities and mitigating radiation hazards in deep space missions.

ESCAPADE is a twin-spacecraft low-cost Mars mission that will revolutionize our understanding of how space weather conditions drive magnetic structure and flows of energy and momentum throughout Mars’ unique hybrid magnetosphere, and how this interaction drives both ion escape and sputtering escape. ESCAPADE will measure magnetic field strength and topology, suprathermal ion distributions and electron flows, and thermal electron and ion densities, as well as possibly image visible aurora. Our 2-part scientific campaign of temporally and spatially-separated multipoint measurements in different regions of Mars’ diverse plasma environment, will allow us to untangle spatial from temporal variability, characterize short-term variability, and unravel the cause-and-effect of solar wind control of magnetospheric structure and ion and sputtering escape for the first time.ESCAPADE launched on November 13, 2025. Though it is a Mars mission, ESCAPADE’s journey begins with a 12 month “loiter” phase within ~2.5 million km of earth, primarily on the anti-sunward side, looping around the L2 Lagrange point and passing twice through the Earth’s magnetotail, at ~320 and again at ~80 earth radii. Instruments are due to be turned on in late February 2026, just prior to this first tail passage. ESCAPADE will provide the first two-point measurements of heliospheric conditions in these regions of space, addressing questions of solar wind and space weather structure on ~105 km scales and investigating distant magnetotail features, including spatial extent, dependence on solar wind conditions, and the existence of reconnection in the distant magnetotail. In November 2026, ESCAPADE will execute Oberth maneuvers at a ~500 km perigee to start their interplanetary journey, arriving at Mars in September 2027 and beginning their science mission in spring 2028. This presentation will focus on first results from the plasma instruments in the near-Earth heliospheric environment.

The Martian magnetotail is a dynamic region where several processes contribute to plasma acceleration. Here, we analyze years of Mars Atmosphere and Volatile EvolutioN (MAVEN) data to evaluate the role of magnetic tension forces in driving plasma acceleration within current sheets in the tail. Based on magnetic field measurements, we identify 547 current sheet crossings that follow a Harris profile and find that the median observed current sheet density is 110 nA , with a typical sheet width of 100 km. We estimate a median normalized of 0.1, and force of N , capable of accelerating planetary ions within the sheets to 1 keV over 2 . We also analyze plasma energization signatures in nine high‐ case studies and find they can be explained by work done by , although observed ion differential streaming suggests additional forces may be present.