| 1 | A | B | C |
| --- | --- | --- | --- |
| 2 | Planets beyond Neptune - Pluto loses Planet X title |  |  |
| 3 | Year | Mass | Notes |
| 4 | 1931 | 1 Earth | Nicholson & Mayall |
| 5 | 1942 | 0.91 Earth | Wylie |
| 6 | 1948 | 0.1 (1/10 Earth) | Kuiper |
| 7 | 1973 | 0.025 (1/40 Earth) | Rawlins |
| 8 | 1976 | 0.01 (1/100 Earth) | Cruikshank, Pilcher, & Morrison |
| 9 | 1978 | 0.002 (1/500 Earth) | Christy & Harrington |
| 10 | 2006 | 0.00218 (1/459 Earth) | Buie et al. |

Question: What were the earliest measurements of the mass of Neptune?
Answer: In 1931, Nicholson and Mayall calculated Neptune's mass to be equal to 1 Earth, a value similar to the 0.91 Earth mass calculated in 1942 by Lloyd R. Wylie.