Stairways to climate stability.[ILLUSTRATION OMITTED] They may not be the steps to paradise, but several outcrops of Martian rocks (shown at left) do resemble stairs, displaying a pattern that suggests the ancient climate on the Red Planet wasn't always an amalgam of cataclysmic cat·a·clysm n. 1. A violent upheaval that causes great destruction or brings about a fundamental change. 2. A violent and sudden change in the earth's crust. 3. A devastating flood. floods, volcanic eruptions volcanic eruptions discharging of fumes, dust and lava from volcanoes. They have damaging potential in addition to those of being physically overpowering by the lava flow or the ash or dust fallout. and crater-gouging impacts. Instead, the evenly spaced, eons-old sedimentary rock sedimentary rock: see rock; sediment. sedimentary rock Rock formed at or near the Earth's surface by the accumulation and lithification of fragments of preexisting rocks or by precipitation from solution at normal surface temperatures. layers in the Arabia Terra Arabia Terra is a large upland region in the north of Mars. It is densely cratered and heavily eroded. This battered topography indicates great age, and Arabia Terra is presumed to be one of the oldest terrains on the planet. region imply that during a brief time several billion years ago, the climate varied in a gentler, more predictable fashion--changes that may have been tied to variations in the planet's tilt. Evidence indicates that Mars' spin axis has wobbled significantly in the last several million years, periodically cooling the equatorial region and warming the poles as they received more sunlight. The new findings hint that the axis may have had a similar wobble wobble /wob·ble/ (wob´'l) to move unsteadily or unsurely back and forth or from side to side. See under hypothesis. wob·ble n. 1. in the much more distant past, notes Kevin Lewis of Caltech. Lewis and his colleagues describe those findings, based on images taken by the Mars Reconnaissance Orbiter's HiRISE camera, in the Dec. 5 Science. |
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