The geologically supervised spectral investigation as a key methodology
for identifying volcanically active areas on Venus
Abstract
Combining geologic mapping and stratigraphic reconstruction of lava
flows at Sapas, Maat and Ozza Montes, three potentially young volcanic
structures of Atla Regio on Venus, with analysis of the spectral
signature (radar emissivity anomalies) characterizing each mapped flow,
Brossier et al. (2021) conclude that some of the lava flows at Maat Mons
may be geologically recent (~25 Ma). The lava flows of
Sapas and Ozza Montes are more consistent with weathered lava flows
forming chlorapatite and some perovskite oxides. We discuss the reasons
why, besides the importance of the results they obtained, the
methodology they used can be very valuable for future investigations
with higher resolution datasets. The importance of combining geologic
interpretation with spectral analysis in the reconstruction of the
volcanic history of Venus Considering its size, gravity and the presence
of an atmosphere, Venus is typically considered as the twin sister of
the Earth, but despite the apparent similarities with our planet, Venus
is notably different because it is characterized by its extreme surface
environment. With 90 bars and 475 °C, its surface is a very inhospitable
place for life as we know it. Venus does not show evidence for a present
plate tectonics-like activity, having a major part of its surface
volcanic deposits younger than 300 Ma. It has been hypothesized that
Venus underwent a catastrophic event of global resurfacing about 300 Ma
ago, which may have almost entirely rejuvenated its surface (Schaber,
1992; Nimmo and McKenzie, 1998; Romeo and Turcotte, 2010; Strom et al.,
1994; Turcotte et al., 1999). Some other studies instead favor a more
equilibrium resurfacing model of the surface (Phillips et al, 1992;
Phillips and Hansen, 1994; Bjonnes et al., 2012; O’Rourke and Korenaga,
2015). It is also possible that the past volcanic history of Venus
somehow reflected an intermediate situation between these two end-member
scenarios. Related to this topic, there has been a subject of debate
whether or not the volcanism on Venus is currently evolving toward an
equilibrium stage, with occurrences of smaller and more frequent
localized eruptions. In this regard, it is vital to identify areas with
current or recent volcanism, to measure the actual rate and volume of
the most recent volcanic eruptions. The geologic interpretation and
analysis of spectral signatures (both in radar and infrared wavelengths)
can help us constraining the age of surface volcanic deposits on Venus.
In geology, the so called “cross-cutting interrelationships” can
constrain the relative age of two lava flows as it has been applied to
young, possibly very recent lava flows and tectonic features on