Near‐Ultraviolet to Near‐Infrared Spectral Properties of Hollows on Mercury: Implications for Origin and Formation Process

Abstract

Although the spectral signatures are few, the surface of Mercury is spectrally and morphologically diverse. Based on spectral variation and morphology, two main terrain types and several smaller units have been identified at the surface of Mercury (

Present Day Endogenic and Exogenic Activity on Mercury

“…Hollows preferentially occur in low reflectance material (LRM; ∼30% lower than the already dark global average reflectance) (Robinson et al, 2008) and on the floor, central peak, rim, or the ejecta deposit of large craters or basins. Previous studies suggested that hollows could result from the sublimation of volatile-bearing materials such as sulfides, space weathering, outgassing, and pyroclastic volcanism (Barraud et al, 2020;Blewett et al, 2011Blewett et al, , 2013. Additionally, their crisp features and lack of superimposed craters indicate that they are the youngest non-impact features on Mercury (Blewett et al, 2018).…”

Spectral investigation of Mercury's pits' surroundings: Constraints on the planet's explosive activity

“…A first step consists in removing the outliers deviating by more than 2 sigma. Only the most distant outliers are removed using this method, which represents less than 1% of the measurements by the VIS detector and less than 4% in the NIR (Barraud et al, 2020). In a second step, a moving average window of 3 points is applied to the entire VIS and NIR, reducing the scatter of the channel-to-channel reflectance.…”

Low sulfide concentration in Mercury’s smooth plains inhibits hollows

“…However, this absorption feature was not observed in all hollows of Mercury ( 9 ), which further complicate the determination of the nature and composition of the volatile species truly responsible for their formation. Reflectance spectra of hollows obtained by the Visible and Infrared Spectrograph (VIRS), component of the Mercury Atmospheric and Surface Spectrometer (MASCS) onboard MESSENGER, lack similar absorption features despite its higher spectral resolution ( 14 ). In particular, hollows within Hopper crater exhibit a weak absorption feature between 559 and 828 nm in multispectral data ( 9 ), but no absorption band above the noise of MASCS/VIRS is observed in the reflectance spectra of these hollows ( 14 ).…”

“…Reflectance spectra of hollows obtained by the Visible and Infrared Spectrograph (VIRS), component of the Mercury Atmospheric and Surface Spectrometer (MASCS) onboard MESSENGER, lack similar absorption features despite its higher spectral resolution ( 14 ). In particular, hollows within Hopper crater exhibit a weak absorption feature between 559 and 828 nm in multispectral data ( 9 ), but no absorption band above the noise of MASCS/VIRS is observed in the reflectance spectra of these hollows ( 14 ). Nonetheless, MASCS/VIRS spectra show a strong concave curvature between 300 and 600 nm, unique to hollow material ( 14 ).…”

“…In particular, hollows within Hopper crater exhibit a weak absorption feature between 559 and 828 nm in multispectral data ( 9 ), but no absorption band above the noise of MASCS/VIRS is observed in the reflectance spectra of these hollows ( 14 ). Nonetheless, MASCS/VIRS spectra show a strong concave curvature between 300 and 600 nm, unique to hollow material ( 14 ). Here, we present a comparison and spectral modeling between MASCS/VIRS spectra of hollows and laboratory spectra of Mercury’s analogs.…”