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Husain, L.

Publications and source records attributed to Husain, L..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Ar-40/Ar-39 age of the Shergotty achondrite and implications for its post-shock thermal history

Ar-40/Ar-39 measurements are used to determine the age of the Shergotty achondrite and the chronology of the shock event responsible for the complete conversion of its plagioclase to maskelynite is discussed. Apparent ages are found to vary between 240 and 640 million years for the whole rock sample, with a plateau age of 254 million years for a maskelynite separate. The Rb-Sr age of 165 million years determined by Nyquist at al (1978) suggests that the maskelynite as well as the whole rock was incompletely degassed. Argon diffusion characteristics indicate a post-shock cooling time greater than 1000 years and a burial depth greater than 300 m for a thermal model of a cooling ejecta blanket of variable thickness. It is concluded that the shock event which degassed the argon and reset the Rb-Sr systematics occurred between 165 and 250 million years ago when the parent body experienced a collision in the asteroid belt.

Bogard, D. D.↗
NASA NTRS1977

A new 1.3 Aeon-Young achondrite

The Ar-40/Ar-39 age of Governador Valadares, a Nakhlite achondrite, has been determined to be 1.32 plus or minus 0.04 billion yrs. The K-Ar age and cosmic-ray exposure age of Governador Valadares are essentially identical to analogous ages for the two other known Nakhlite achondrites and to Rb-Sr ages determined for Nakhla. These data suggest that all three known meteorites of this class were derived from the same parent body by a common event, and confirm that Governador Valadares is a member of this class. The most probable heat source for producing such meteorites may be collisional melting of a portion of the parent body. Nakhlites may represent a rare phenomenon and may not be at all representative of the surface of their parent body.

Bogard, D. D.↗
NASA NTRS1976

Ar-40/Ar-39 dating of collisional events in chondrite parent bodies

Ar-40/Ar-39 age dating of a number of shocked ordinary chondrites is interpreted in terms of collisional degassing events of meteorite parent bodies, probably in the asteroid belt. Examples of L, H, and at least one LL chondrite show episodic degassing. Degassing ages suggest several distinct events ranging from about 0.03 aeon to 0.7 aeon and probably higher. All specimens of either the H or L chondrites are not consistent with a single age event. A direct correlation exists between the degree of shock heating and the fraction of argon lost during degassing. However, no chondrite yet analyzed shows complete degassing of its high-temperature phase. Consequently, whole rock K-Ar ages are not accurate monitors of the time of the shock event.

Bogard, D. D.↗
NASA NTRS1976

The duration of volcanism in Mare Serenitatis

The crystallization ages of a suite of Apollo 17 basalts from four different stations have been measured using the Ar-39 to Ar-40 stepwise heating technique. The rocks analyzed include all principal petrographic types found at Apollo 17 landing site. A correlation between the ages and the petrographic type exists; plagioclase-poikilitic ilmenite basalts are youngest and olivine porphyritic ilmenite basalts are the oldest. The duration of volcanism in Mare Serenitatis is about 200 million years, the same as observed for Mare Imbrium, and less than observed for Mare Tranquillitatis, 400 million years. A relationship between duration of volcanism and gravity anomalies is noted. The cosmic ray exposure ages (in millions of years) for various locations range as: station 4, 58-315; station 5, 85-440; station 6, 110; station 8, 90-160.

Schaeffer, O. A.↗
NASA NTRS1976

Ages of highland rocks - The chronology of lunar basin formation revisited

The Ar-39-Ar-40 age studies are presented for thirteen Apollo 16 and 17 highland rocks. The plateau ages range from 3.63 to 4.23 G.y. for ten of the samples which give plateaus. For three of the samples, a Ar-39-Ar-40 age is not obtainable because there is no plateau in the temperature release patterns. The ages of all Ar-39-Ar-40 lunar highland rocks are summarized in histograms for Apollo 16 and 17. The histograms show a preponderance of ages in the 3.95 plus or minus 0.05 G.y. interval with a fair number of ages well in excess of 4.0 G.y. up to 4.3 G.y. The ages of the highland rocks indicate a more or less continuous bombardment of the lunar surface during the first 600 m.y. with the major ring basins being formed randomly during this period and not all in a relatively short interval at 3.9-4.0 G.y. ago.

Schaeffer, O. A.↗
NASA NTRS1975

Lunar evolution - The first 600 million years

From a stepwise-heating experiment on neutron-irradiated samples of whole rock and a plagioclase separate, an Ar-40/Ar-39 age of 4.26 plus or minus 0.02 G.y. was determined for the Apollo 17 troctolite 76535. This rock is believed to have formed as a result of very slow cooling at a depth of 10 to 40 km, and hence furnishes direct evidence that the moon was chemically zoned before 4.26 G.y. The age of the rock is associated with the Serenitatis Basin forming event. The formation of the Serenitatis Basin is then deduced to have occurred 4.26 plus or minus 0.02 G.y. ago, about 300 m.y. before the Imbrium event. It appears that the major basin forming era on the near side of the moon lasted longer than 300 m.y. The grouping of many lunar rock ages at 3.9 to 4.0 G.y. is most likely due to the fact that the Imbrium ejecta predominates all highland landing sites.

Husain, L.↗
NASA NTRS1974

Ar-40/Ar-39 chronology and cosmic ray exposure ages of the Apollo 15 samples

The Ar-40*/Ar-39* thermal release patterns of igneous soil fragments, rake basalts, and large crystalline rocks are by and large well defined. Shock deformations of up to moderate intensities have no observable effects on the Ar-40*/Ar-39* release patterns. Neither do the Ar-40* diffusion losses have any relationship with the shock intensities. The peak of the magnetic activity in Palus Putredinis occurred at 3.33 plus or minus 0.02 Gy, lava flows continuing up to 3.13 Gy but at much reduced intensity. No correlation between the crystallization ages and the petrographic rock types was observed. The cosmic ray exposure gas indicate a mature regolith around the Hadley Rille-Apennine Front region. The exposure ages of the Apollo 15 samples cannot reliably be used to obtain the time of prominent cratering events at this site.

Husain, L.↗
NASA NTRS1974

Chronology of lunar basin formation

The lunar anorthositic rocks 60025,86 and 60015,22 give Ar-40/Ar-39 ages of about 4.19 and 3.50 b.y., respectively. Two coarse fine anorthositic rock fragments 78503,7,1 and 72503,8,12 have ages of 4.13 and 3.96 b.y., respectively. The rock 60025 is the first large lunar rock with an age well in excess of 4.0 b.y. Evidence for the conclusion that the cratering events reset the radiometric ages is discussed. The chronology of the lunar basin forming events is deduced from the ages of the lunar highland impact breccias. Using the ages of lunar breccias, we have deduced a chronology for the last five lunar basin forming events. It is concluded that the 'lunar cataclysm' is the Imbrium event.

Schaeffer, O. A.↗
NASA NTRS1973

Lunar volcanism - Age of the glass in the Apollo 17 orange soil.

Glasses on the moon can form either by impact or by volcanic processes. An age determination indicates that the glass of the orange soil formed close in time to the volcanic activity in the Sea of Serenity about 3,750 million years ago. The orange soil was certainly not formed by a recent fumarole. The young exposure age, about 32 million years, found for the glass of the orange soil is in agreement with its fresh appearance on the lunar surface.

Husain, L.↗
NASA NTRS1973

Early lunar history - Ages of 2 to 4 mm soil fragments from the lunar highlands

The ages of twenty-one 2 to 4 mm soil fragments from Apollo 16 stations 6, 8, 11, and 13, including all six major petrographic rock types found among Apollo 16 samples, were determined using the Ar-40/Ar-39 stepwise-heating technique. Twelve of the twenty-one samples have ages within 3.95 to 4.06 billion years, and it is believed that they represent the age of at least one stage of the Cayley Formation. Four samples have ages distinctly older than 4.00 billion years, making them the oldest lunar material found to date.

Schaeffer, O. A.↗
NASA NTRS1972

Age of a lunar anorthosite.

The crystallization age of an Apollo 15 anorthosite rock, 15415,9, returned from the lunar highlands has been measured to be 4.09 (plus or minus 0.19) b.y. The primitive lunar crust must have been formed in the first 300 to 400 m.y. The results give some credence to the hypothesis that the primitive lunar surface was molten and large-scale fractional crystallization occurred in the early history of the moon.

Husain, L.↗
NASA NTRS1972

The ages of lunar material from Fra Mauro, Hadley Rille, and Spur Crater.

Ar-40/Ar-39 dating techniques were applied to estimate the age of twelve crystalline and fragmented Fra Mauro rock samples and six Hadley Rille and Spur Crater rock samples provided by the Apollo 14 and 15 missions. Genesis histories of some associated lunar surface features are traced back on the basis of obtained rock age values.

Husain, L.↗