An ancient lunar magnetic dipole field

摘要: SINCE the landing of first Luna spacecraft it has been known that present magnetic moment Moon is negligible. Later, Explorer 35 data1 gave an upper limit 4 γ (= nT) to dipole field at surface. Now, Russell et al.2 by analysing Apollo 15 subsatellite magnetometer data obtained during passages through geomagnetic tail (where reasonably steady) have calculated 0.05 γ. They shown both induced and permanent moments can be determined separately north south lobes tail, in which directed towards away from Sun, respectively. Only component plane orbit determinable less than 1.3 × 1018 gauss cm3: unlikely perpendicular appreciably greater. estimated error 1.33 cm3, therefore concluded lunar not significantly different zero. Paradoxical as may seem, follows this observation possessed a internal origin its early history.