Martian layered ejecta craters are theorized to form by tapping into water ice. The inference that some equatorial layered ejecta craters are Amazonian indicates ice has persisted in the tropics. However, detailed spatial and temporal distribution and evolution of this ice remains unknown; which is critical to constraining Mars’ global water cycle and climate change over eons. Here we estimate absolute model formation ages for layered and radial (ballistic) ejecta craters to constrain the spatial and temporal distribution of equatorial ice. The assumption is radial ejecta form where volatiles are not present in significant quantities. Ages are derived from the density of smaller craters superposed on the ejecta blankets. We examine 73 craters in a 30° x 30° area centered at 15ºS, 355ºE, with 44 layered and 29 radial ejecta. Analysis suggests an increasing proportion of layered ejecta craters with increasing diameter. This trend is amplified when considering younger (<3.4 Ga) craters only andwould be in agreement with deeper tropical subsurface ice and a receding ice table. Conversely, it could indicate “armoring” preserves layered over radial ejecta. Layered and radial ejecta craters are mixed over distances comparable to their diameters, which represents an unreasonably short length scale for ground-ice emplacement. This supports intermittent low-latitude surface ice—from excursions to high obliquity—could be responsible. The combination of increasing proportion of layered ejecta with crater size and random spatial distribution may suggest a hybrid model in which buried ice and intermittent, but extensive, tropical glaciers both contribute to layered ejecta crater formation.

The magnetometer of the InSight mission operated on the martian surface from November 2018 until May 2022. Previously, satellites have provided information on the martian magnetic field environment from orbit, however, the degree to which external fields penetrate to and interact with the surface could not be studied prior to the InSight landing. Here, we present an overview of the complete surface magnetic field data from InSight sols 14 to 1241 that display different external magnetic field phenomena, transient and periodic. Periodic observations range from short period waves (100s-1000s of seconds), diurnal variations, ~26 sol Carrington rotations, to seasonal fluctuations. Transient events are observed in response to space weather and dust movement. We find that ionospheric variations are the dominant contribution as seen from the surface, while contributions from the undisturbed IMF are more subtle. We discuss limitations associated with a single point measurement and opportunities that future missions could enable. Including magnetometers on future missions at a variety of locations for long-duration continuous observations will be of great value in understanding a range of external field phenomena and will enable further investigations in different crustal magnetic field settings.