Some unique surface patterns on ignimbrites on Earth: A 'bird's eye' view as a guide for planetary mappers

摘要

Observations of terrestrial analogs are critical to aiding planetary mappers in interpreting surface lithologies on other planets. For instance, the presence of ignimbrites on Mars has been debated for over three decades and is supported by analogy with deposits on Earth. Critical evidence includes the geomorphic and surface expression of the deposits, and those in the Central Andes of South America are amongst the most-cited analogs. Herein we describe some prominent surface textures and patterns seen in ignimbrites on the scale of high-resolution remotely sensed data (10-1 m per pixel). These include pervasive joints and fractures that contribute to yardang form and development as well as prominent mounds, fissures, and fracture networks ("spiders", "bugs", "boxworks") on ignimbrite surfaces. While all these features are related to intrinsic cooling and degassing processes, the involvement of external water buried by hot pyroclastic flows enhances fumarolic activity, advective cooling, and joint development. Observations of these geomorphic expressions using remote sensing are only possible with the highest resolution data and limited surface erosion. For Mars, where similarly high resolution datasets are available (for example, the High Resolution Imaging Sensor Experiment or HiRISE) extensive dust cover may limit the recognition of similar features there. However significant relief on some of these features on Earth indicate they might still be detectable on Mars. (C) 2017 Elsevier B.V. All rights reserved.