Field investigation of dried lakes in western United States as an analogue to desiccation fractures on Mars

Potential Desiccation Polygons (PDPs), tens to hundreds of meters in size, have been observed in numerous regions on Mars, particularly in ancient (>3Gyr old) terrains of inferred paleolacustrine/playa geologic setting, and in association with hydrous minerals such as smectites. Therefore, a better understanding of the conditions in which large desiccation polygons form could yield unique insight into the ancient climate on Mars. Many dried lakebeds/playas in western United States display large (>50m wide) desiccation polygons, which we consider to be analogues for PDPs on Mars. Therefore, we have carried out fieldwork in seven of these dried lakes in San Bernardino and the Death Valley National Park regions complemented with laboratory and spectral analysis of collected samples. Our study shows that the investigated lacustrine/playa sediments have (a) a soil matrix containing 40-75% clays and fine silt (by volume) where the clay minerals are dominated by illite/muscovite followed by smectite, (b) carbonaceous mineralogy with variable amounts of chloride and sulfate salts, and significantly, (c) roughly similar spectral signatures in the visible-near-infrared (VIS-NIR) range. We conclude that the development of large desiccation fractures is consistent with water table retreat. In addition, the comparison of the mineralogical to the spectral observations further suggests that remote sensing VIS-NIR spectroscopy has its limitations for detailed characterization of lacustrine/playa deposits. Finally, our results imply that the widespread distribution of PDPs on Mars indicates global or regional climatic transitions from wet conditions to more arid ones making them important candidate sites for future in situ missions.

American spiders and their spinningwork. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits. By Henry C. McCook.

v.2 1890

American spiders and their spinningwork. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits. By Henry C. McCook.

v.3 1893

American spiders and their spinningwork. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits. By Henry C. McCook.

v.3

American spiders and their spinningwork. A natural history of the orbweaving spiders of the United States, with special regard to their industry and habits. By Henry C. McCook.

v.2

The Turkish Empire in Europe, Asia, and Africa: dividid into all its governments, together with the other territories that are tributary to it, as also the dominions of ye Emperor of Marocco [sic] according to the newest and most exact observations

by H. Moll.

Public health personnel in the United States, 1980 : second report to the Congress of the Secretary of Health and Human Services as required by section 793 of the Public Health Service Act.

Mode of access: Internet.

Biographical directory of the American Congress, 1774-1961 : the Continental Congress, September 5, 1774, to October 21, 1788 and the Congress of the United States, from the First to the Eighty-sixth Congress, March 4, 1789, to January 3, 1961, inclusive.

"This volume, compiled by Clifford P. Reynolds, publications technician of the [Joint] Committee [on Printing], is a revision of the Dictionary of the United States Congress and the general government, published in 1859 and again revised in 1869, by Charles Lanman; the Biographical annals of the civil government of the United States in 1876, by Joseph Lanman and James Anglin, and the Lanman edition of 1876 as corrected by Joseph M. Morrison in 1887; the Political register and congressional directory of 1878; by Ben: Perley Poore; the Biographical congressional directory of 1903, by O. M. Enyart; the Biographical congressional directory in 1911, the Biographical directory of the American Congress of 1927, by Ansel Wold, and the 1949 edition by James L. Harrison."

Message from the President of the United States communicating in answer to a Senate resolution of December 6, 1877 information in relation to the operation of the Union Pacific Railroad and its branches.

Signed: Charles Devens, Attorney-General.

Administration of the office of the alien property custodian. Message from the President of the United States transmitting in response to Senate resolution no. 299, a copy of the report made by the comptroller general to the President of the United States relative to his investigation of the administration of the office of the alien property custodian.

Read; referred to the Committee on the judiciary and ordered printed, December 22, 1926.

Economic conditions of the Virgin Islands. Supplemental report on an investigation of the economic conditions of the Virgin Islands of the United States with special reference to the currency situation and the possibility of establishing an American bank,

Presented by Mr. Willis. Ordered to be printed May 10 (calendar day, May 12), 1926.

Mutual security act of 1951 : hearings before the Committee on Foreign Relations and the Committee on Armed Services, United States Senate, Eighty-second Congress, first session, on S. 1762, a bill to promote the foreign policy and provide for the defense and general welfare of the United States by furnishing assistance to friendly nations in the interest of international security.

Hearings held: July 26-Aug. 9, 1951.