Author/Authors :
Shepard، نويسنده , , Michael K. and Clark، نويسنده , , Beth Ellen and Nolan، نويسنده , , Michael C. and Howell، نويسنده , , Ellen S. and Magri، نويسنده , , Christopher and Giorgini، نويسنده , , Jon D. and Benner، نويسنده , , Lance A.M. and Ostro، نويسنده , , Steven J. and Harris، نويسنده , , Alan W. and Warner، نويسنده , , Brian and Pray، نويسنده , , Donald and Pravec، نويسنده , , Petr and Fauerbach، نويسنده , , Michael and Bennett، نويسنده , , Thomas and Klotz، نويسنده , , Alain and Behrend، نويسنده , , Raoul and Correia، نويسنده , , Horacio and Coloma، نويسنده , , Josep and Casulli، نويسنده , , Silvano and Rivkin، نويسنده , , Andrew، نويسنده ,
Abstract :
We observed ten M- and X-class main-belt asteroids with the Arecibo Observatoryʹs S-band (12.6 cm) radar. The X-class asteroids were targeted based on their albedos or other properties which suggested they might be M-class. This work brings the total number of main-belt M-class asteroids observed with radar to 14. We find that three of these asteroids have rotation rates significantly different from what was previously reported. Based on their high radar albedo, we find that only four of the fourteen—16 Psyche, 216 Kleopatra, 758 Mancunia, and 785 Zwetana—are almost certainly metallic. 129 Antigone has a moderately high radar albedo and we suggest it may be a CH/CB/Bencubbinite parent body. Three other asteroids, 97 Klotho, 224 Oceana, and 796 Sarita have radar albedos significantly higher than the average main belt asteroid and we cannot rule out a significant metal content for them. Five of our target asteroids, 16 Psyche, 129 Antigone, 135 Hertha, 758 Mancunia, and 785 Zwetana, show variations in their radar albedo with rotation. We can rule out shape and composition in most cases, leaving variations in thickness, porosity, or surface roughness of the regolith to be the most likely causes. With the exception of 129 Antigone, we find no hydrated M-class asteroids (W-class; Rivkin, A.S., Howell, E.S., Lebofsky, L.A., Clark, B.E., Britt, D.T., 2000. Icarus 145, 351–368) to have high radar albedos.
