from Part V - Synthesis
Published online by Cambridge University Press: 10 December 2009
Abstract
Orbital and landed missions have demonstrated that Mars possesses an extensive and diverse sedimentary rock record that is mostly ancient. Many observed or inferred processes appear familiar to sedimentary geologists but, in detail, the sedimentary record of Mars differs in fundamental ways from the terrestrial record. Mars is a basaltic planet and accordingly, the provenance of sedimentary material, including particulate debris and aqueous fluids from which chemical constituents precipitate, is composed of basalt rather than intermediate to felsic igneous compositions characteristic of terrestrial upper continental crust. Aqueous alteration, observed on Mars and studied experimentally, indicates surficial processes dominated by low pH; under acidic conditions, many chemical relationships that are characteristic of terrestrial weathering do not apply. Aluminum and Fe are far more soluble and mobile, Si mobility is limited by fluid/rock ratio and iron oxidation rates are sluggish. Low fluid/rock ratios are indicted by the observation that only the most soluble minerals (olivine, Fe-Ti oxides, phosphates, possibly pyroxene) appear to be widely involved in surface alteration with little evidence for involvement of relatively insoluble plagioclase. An intriguing result, from both global-scale orbital and detailed surface spectroscopy, and geochemistry obtained by rovers, is that evaporitic processes, leading to a wide variety of Ca-, Mg- and Fe-bearing sulfates in sedimentary rocks, alteration profiles, and soils, appear to have been common throughout Martian geological history. Investigations by Spirit and Opportunity demonstrate that classical stratigraphy and sedimentology can be accomplished on the Martian surface using remote techniques.
To save this book to your Kindle, first ensure no-reply@cambridge-org.demo.remotlog.com is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.