We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations...We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations from CanariC am on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia,roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1σ scale of Γ = 100（-52）^（＋100）＋Jm^（-2）s^-0.5K^-1, fr = 0.78~1.0, pv = 0.286（-0.026）^（＋0.030） and D（eff） = 378（-25）^（＋19）m, and 3σscale of Γ = 100（-100）^（＋240）Jm^（-2）s^-0.5 K^-1, fr = 0.2~1.0, pv = 0.286（-0.029）^（＋0.039） and D（eff） = 378（-29）^（＋27） m. The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 11473073, 11403105, 11633009 and 11661161013)the Science and Technology Development Fund of Macao (Grant Nos. 039/2013/A2 and 017/2014/A1)+2 种基金the innovative and interdisciplinary program by CAS (Grant No. KJZDEW-Z001)the Natural Science Foundation of Jiangsu Province (Grant No. BK20141509)the Foundation of Minor Planets of Purple Mountain Observatory
文摘We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations from CanariC am on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia,roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1σ scale of Γ = 100（-52）^（＋100）＋Jm^（-2）s^-0.5K^-1, fr = 0.78~1.0, pv = 0.286（-0.026）^（＋0.030） and D（eff） = 378（-25）^（＋19）m, and 3σscale of Γ = 100（-100）^（＋240）Jm^（-2）s^-0.5 K^-1, fr = 0.2~1.0, pv = 0.286（-0.029）^（＋0.039） and D（eff） = 378（-29）^（＋27） m. The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.
