Faults network on Enceladus North Pole

Abstract:

With a mean radius of 252 km, Enceladus is the second smallest spherical moon of Saturn but is the most active icy-moon of the solar system. During its 13 years of mission, Cassini was able to image and sample its South pole plumes with great details and reveal the presence of 4 major faults, the Tiger Stripes, that continuously eject materials from the inner ocean located a few kilometers beneath the surface [1]. Such activity was not reported at the North Pole which is heavily cratered.

In this study, we report the presence of 2 major stripes at the North Pole, 3 times smaller than their counterpart at the South Pole. They form a X-shape slightly offset by a few degrees from the planetographic North Pole.This network of faults is 100 km long, up to 4 km wide, with an estimated shear of 3 km [2].

No active plume are reported, however, using very-high resolution Cassini-VIMS observations (at 2 km/pixel), we clearly observe a local increase of the 1.04, 1.25, 1.5 and 2.0 µm band depths on the faults [3]. This signature is known to be associated with an increase of the grain size of the ice, analog to the one observed at the South Pole [4-7]. The presence of a Fresnel peak at 3.1 µm also indicates the presence of crystalline in this region [8]. Finally, due to its lower signature, we might have a small signal of CO₂ at 4.26 µm [9].

These observations are consistent with a global ocean underneath Enceladus ice shell [10] and provide additional constrains about its thickness at the North Pole.

References: [1] Porco et al. (2006) [2] Bland et al. (2018) [3] Robidel et al. (2020) [4] Jaumann et al. (2008) [5] Newman et al . (2008) [6] Taffin et al. (2012) [7] Scipioni et al. (2017) [8] Hansen and McCord (2004) [9] Combe et al. (2019) [10] Choblet et al. (2017)