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Post Info TOPIC: Asteroid 2008 EV5
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Title: Composition of Near-Earth Asteroid 2008 EV5: Potential target for Robotic and Human Exploration
Authors: Vishnu Reddy, Lucille Le Corre, Michael Hicks, Kenneth Lawrence, Bonnie Buratti, Paul Abell, Michael Gaffey, Paul Hardersen

We observed potentially hazardous asteroid (PHA) 2008 EV5 in the visible (0.30-0.92 microns) and near-IR (0.75-2.5 microns) wavelengths to determine its surface composition. This asteroid is especially interesting because it is a potential target for two sample return mission proposals (Marco Polo-R and Hayabusa-2) and human exploration due to its low delta-v for rendezvous. The spectrum of 2008 EV5 is essentially featureless with exception of a weak 0.48-microns spin-forbidden Fe3+ absorption band. The spectrum also has an overall blue slope. The albedo of 2008 EV5 remains uncertain with a lower limit at 0.05 and a higher end at 0.20 based on thermal modelling. The Busch et al. (2011) albedo estimate of 0.12 is consistent with our thermal modelling results. The albedo and composition of 2008 EV5 are also consistent with a C-type taxonomic classification (Somers et al. 2008). The best spectral match is with CI carbonaceous chondrites similar to Orgueil, which also have a weak 0.48-microns feature and an overall blue slope. This 0.48-microns feature is also seen in the spectrum of magnetite. The albedo of CI chondrites is at the lower limit of our estimated range for the albedo of 2008 EV5.

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Title: Radar Observations and the Shape of Near-Earth Asteroid 2008 EV5
Authors: Michael W. Busch, Steven J. Ostro, Lance A.M. Benner, Marina Brozovic, Jon D. Giorgini, Joseph S. Jao, Daniel J. Scheeres, Christopher Magri, Michael C. Nolan, Ellen S. Howell, Patrick A. Taylor, Jean-Luc Margot, Walter Brisken

We observed the near-Earth asteroid 2008 EV5 with the Arecibo and Goldstone planetary radars and the Very Long Baseline Array during December 2008. EV5 rotates retrograde and its overall shape is a 400 /pm 50 m oblate spheroid. The most prominent surface feature is a ridge parallel to the asteroid's equator that is broken by a concavity 150 m in diameter. Otherwise the asteroid's surface is notably smooth on decameter scales. EV5's radar and optical albedos are consistent with either rocky or stony-iron composition. The equatorial ridge is similar to structure seen on the rubble-pile near-Earth asteroid (66391) 1999 KW4 and is consistent with YORP spin-up reconfiguring the asteroid in the past. We interpret the concavity as an impact crater. Shaking during the impact and later regolith redistribution may have erased smaller features, explaining the general lack of decameter-scale surface structure.

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The 270 - 600 metre wide asteroid 2008 EV5 will make a close pass (47.1 Lunar Distances, 0.1211 AU), travelling at 4.95 km/s, to the Earth-Moon system on the 2nd July, 2009.

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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).

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Date       UT      R.A. (J2000) Decl.    Delta     r     El.    Ph.   V      
             h m s                                                            
 2008 12 14 000000 10 02 22.6 -35 09 00   0.032   0.986   92.4  85.7  15.5    
 2008 12 15 000000 09 58 43.1 -32 06 56   0.031   0.988   95.4  82.9  15.3    
 2008 12 16 000000 09 54 52.9 -28 42 26   0.029   0.989   98.7  79.7  15.1    
 2008 12 17 000000 09 50 50.5 -24 52 48   0.027   0.990  102.3  76.1  14.8   
 2008 12 18 000000 09 46 34.0 -20 35 28   0.026   0.992  106.3  72.2  14.6   
 2008 12 19 000000 09 42 01.8 -15 48 35   0.025   0.993  110.7  67.9  14.3   
 2008 12 20 000000 09 37 12.1 -10 31 35   0.023   0.994  115.5  63.3  14.1   
 2008 12 21 000000 09 32 03.1 -04 45 56   0.023   0.995  120.5  58.3  13.9   
 2008 12 22 000000 09 26 32.9 +01 24 09   0.022   0.997  125.7  53.2  13.7   
 2008 12 23 000000 09 20 39.8 +07 51 21   0.022   0.998  130.9  48.1  13.5   
 2008 12 24 000000 09 14 22.0 +14 25 47   0.022   0.999  135.8  43.3  13.3   
 2008 12 25 000000 09 07 38.2 +20 56 12   0.022   1.000  140.1  39.1  13.3   
 2008 12 26 000000 09 00 26.9 +27 11 43   0.022   1.002  143.6  35.7  13.2   
 2008 12 27 000000 08 52 47.3 +33 03 29   0.023   1.003  146.0  33.3  13.2   
 2008 12 28 000000 08 44 38.9 +38 25 34   0.024   1.004  147.3  31.9  13.3   
 2008 12 29 000000 08 36 01.6 +43 15 04   0.026   1.005  147.7  31.5  13.4   
 2008 12 30 000000 08 26 56.1 +47 31 33   0.027   1.006  147.3  31.9  13.5   
 2008 12 31 000000 08 17 23.9 +51 16 22   0.029   1.007  146.3  32.8  13.7


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Asteroid 2008 EV5 was discovered by the Mt. Lemmon Survey on the 4th March 2008.
The (H=19.8) 310 - 700 metre wide asteroid will flyby the Earth-Moon system on the 23rd December, 2008, by 8.4 lunar distances (0.0216 AU).
The maximum predicted brightness is magnitude 13.
Orbital and Physical Characteristics:  
 Orbit type               Aten
 Semimajor axis           0.960444 AU     
 Eccentricity             0.083813        
 Inclination              7.427°       
 Perihelion distance      0.880 AU     
 Aphelion distance        1.051 AU     
 Absolute magnitude (H)   19.8
 Diameter                 310 - 700 meters
 Rotation period          unknown
 Pole direction           unknown
 Lightcurve amplitude     unknown
 Spectral class           unknown
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Orbital Information:
Keplerian elements at epoch 54800 (MJD)


element value 1-sigma variation
a (AU) 0.960444 1.528e-07
eccentricity 0.083813 1.12e-06
inclination
7.427 5.584e-05
Asc. node
93.601 0.0002017
Arg. perih.
236.757 0.000143
M (deg) 89.459 0.0002133

Source

Orbital elements:
2008 EV5                                            PHA, Earth MOID = 0.0096 AU
Epoch 2008 Feb. 24.0 TT = JDT 2454520.5                 MPC
M 157.25327              (2000.0)            P               Q
n   1.06414257     Peri.  235.26532     +0.85581682     +0.50133396
a   0.9501733      Node    94.33736     -0.42292757     +0.82000556
e   0.0923050      Incl.    7.34303     -0.29784197     +0.27614334
P   0.93           H   20.0           G   0.15

From 14 observations 2008 Mar. 4-5.

MPEC 2008 -E47



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