Thomas A. Mutch

The Surface of Mars: The View from the Viking 2 Lander

Viking 2 lander began imaging the surface of Mars at Utopia Planitia on 3 September 1976. The surface is a boulder-strewn reddish desert cut by troughs that probably form a polygonal network. A plateau can be seen to the east of the spacecraft, which for the most probable lander location is approximately the direction of a tongue of ejecta from the crater Mie. Boulders at the lander 2 site are generally more vesicular than those near lander i. Fines at both lander sites appear to be very fine-grained and to be bound in a duricrust. The pinkish color of the sky, similar to that observed at the lander I site, indicates suspension of surface material. However, the atmospheric optical depth is less than that at the lander I site. After dissipation of a cloud of dust stirred during landing, no changes other than those stemming from sampling activities have been detected in the landscape. No signs of large organisms are apparent at either landing site.

The surface of Mars: there view from the viking 1 lander.

The first photographs ever returned from the surface of Mars were obtained by two facsimile cameras aboard the Viking 1 lander, including black-and-white and color, 0.12� and 0.04� resolution, and monoscopic and stereoscopic images. The surface, on the western slopes of Chtyse Planitia, is a boulder-strewn deeply reddish desert, with distant eminences—some of which may be the rims of impact craters—surmounted by a pink sky. Both impact and aeolian processes are evident. After dissipation of a small dust cloud stirred by the landing maneuvers, no subsequent signs of movement were detected on the landscape, and nothing has been observed that is indicative of macroscopic biology at this time and place.

Fine Particles on Mars: Observations with the Viking 1 Lander Cameras

Drifts of fine-grained sediment are present in the vicinity of the Viking 1 lander. Many drifts occur in the lees of large boulders. Morphologic analysis indicates that the last dynamic event was one of general deflation for at least some drifts. Particle cohesion implies that there is a distinct small-particle upturn in the threshold velocity-particle size curve; the apparent absence of the most easily moved particles (150 micrometers in diameter) may be due to their preferential transport to other regions or their preferential collisional destruction. A twilight rescan with lander cameras indicates a substantial amount of red dust with mean radius on the order of 1 micrometer in the atmosphere.

Imaging experiment: The Viking Lander

Abstract The Viking Lander Imaging System will consist of two identical facsimile cameras. Each camera has a high-resolution mode with an instantaneous field of view of 0.04°, and survey and color modes with instantaneous fields of view of 0.12°. Cameras are positioned one meter apart to provide stereoscopic coverage of the near-field. The Imaging Experiment will provide important information about the morphology, composition, and origin of the Martian surface and atmospheric features. In addition, lander pictures will provide supporting information for other experiments in biology, organic chemistry, meteorology, and physical properties.

Abundances of magnetic spherules in Silurian and Permian salt samples.

Abstract Abundances of magnetic spherules in 26 Silurian and Permian salt samples are very similar to abundances in recent collections from the atmosphere. This suggests that meteoritic influx has been constant for the three periods of time sampled.

Craters and associated aeolian features on Mariner 9 photographs - An automated data gathering and handling system and some preliminary results

Craters and associated aeolian features visible on Mariner 9 photographs have been examined. An automated system used to gather, reduce, and store data may have application to other types of planet-wide geological studies. A brief description of the method used to accumulate data is presented, along with some preliminary results for A-frames.

EXTRATERRESTRIAL PARTICLES IN PALEOZOIC SALTS

Introduction In 1876 Murray described small, black, magnetic, spherical particles of probable meteoritic origin that he had extracted from deep-sea sediments. Since that time there have been a number of published reports of presumed extraterrestrial particles collected in a variety of ways. For example, dust falling to the earth’s surface has been trapped and analyzed; many other collections of particles have been obtained from deep-sea sediments and from polar ice caps. All of the samples mentioned reflect influx of material during recent geologic time. Although it is certainly probable that this same dust has been raining down on the earth throughout geologic time, there has been only limited interest in attempts to detect its presence in ancient sedimentary rocks. Crozier (1960 ) analyzed a number of sedimentary materials ranging in age from Recent to Ordovician and found black magnetic spherules in all samples. They were concentrated in numbers ranging from 28 to 240 per gram of sediment and had a size distribution similar to that in atmospheric collections of spherules, also made by Crozier. The majority of particles were smaller than 5,. Hunter and Parkin (1961) describe hollow spherules of magnetite extracted from a Paleogene fine-grained sediment on the island of Barbados. In two samples analyzed the abundance of these spherules was estimated as 14 and 33 per kilogram. A limited number of magnetic spherical particles ranging between 50 and 850, have been recovered from well cuttings and cores of sedimentary rocks of Cretaceous, Miocene, and Pleistocene age (Skolnick, 1961 ) . More recently, Utech (1963) has reported on the distribution of magnetic spherules greater than 7 5 ~ in salts and shales of Permian, Triassic, and Jurassic age. He concluded that these particles fell a t a constant rate during these three periods. In the present study, the first phase of which is reported here, an attempt is being made to examine the complete suite of probable extraterrestrial materials in a number of different Paleozoic, Mesozoic, and Cenozoic salt deposits. Interest has not been arbitrarily confined to spherules of a particular size range, and, in addition to the usual morphological descriptions, chemical and mineralogical analyses have been made.

Sedimentary Patterns in and around Craters from the Pinacate Volcanic Field, Sonora, Mexico: Some Comparisons with Mars

We present results of a reconnaissance study of sedimentary patterns around the Pinacate volcanic field and adjacent Sonora dunes. A cinder cone located in the dunes west of the Pinacates has acted as a sand-migration barrier and has formed a sand-free shadow downwind. This may be analogous to the manner in which dark streaks form downwind of Martian craters. Orbital and aerial photography of the Pinacates suggest that maars adjacent to the Sonora dunes are being infilled by dune sand. However, petrographic data suggest that erosion of friable tuffs and tuff breccias from crater walls is the dominant process filling in all of the craters. The Martian situation is presently less complex than terrestrial examples, such as the Pinacates, since wind seems to be the dominant agent. Water erosion, however, may have been active in past history, and Martian craters may have been modified in a manner analogous to the Pinacate maars.

Intertongued Upper Cretaceous Volcanic and Nonvolcanic Rocks, Central-Western Montana

A thick sequence of intertongued volcanic and nonvolcanic rocks, exposed on the northeast limb of a syncline immediately west of Garrison, central-western Montana, is a western facies of the Elkhorn Mountains Volcanics of Late Cretaceous age. This sequence, here named the Golden Spike Formation, ranges from 4000 to 8000 feet in thickness. In the northwestern sixth of the 9-mile-long outcrop belt, nonvolcanic rocks predominate. Nonvolcanic detritus which forms this relatively thin fluviatile sequence was derived from tectonic uplifts a short distance to the west or northwest of Garrison. In the southeastern area, a relatively thick sequence comprises mostly lavas and volcaniclastic rocks. Most volcaniclastic rocks were probably deposited by epigene processes ( e.g. , weathering, erosion, and redeposition by mudflows, landslides, or running water) and were derived from centers of Elkhorn volcanism to the east. This depositional pattern resulted in intimate interfingering of volcanic and nonvolcanic beds; the authors observed only limited mixing of these two components in individual beds. Throughout the formation many volcanic tongues wedge out within a short distance to the northwest. The virtual absence of volcanic debris in the fluviatile rocks deposited to the northwest indicates either that explosive volcanic activity was minimal in the Elkhorn volcanic field during deposition or that prevailing westerly winds kept pyroclastic material out of the Golden Spike area.

DEFORMATION IN HOST ROCKS ADJACENT TO AN EPIZONAL PLUTON (THE ROYAL STOCK, MONTANA)

Plastic deformation of folds and faults adjacent to the Royal stock, a Laramide epizonal pluton in western Montana, is described. Evidence indicating that this deformation is associated with forceful magmatic intrusion is presented.