The mysterious case of asteroid Oljato's magnetic disturbance
Oljato orbits the Sun once every 3.2 years. During its lifetime, NASA's Pioneer Venus Orbiter observed three passages of Oljato between Venus and the Sun. Each time, there was a marked increase in the region of unusual magnetic peaks known as Interplanetary Field Enhancements (IFEs), both ahead and behind the asteroid. Russell said, "This is not typical asteroidal behaviour! These magnetic increases are rare, occurring in Venus orbit about 10 times per year. Pioneer observed that when Oljato was just in front or just behind Venus, the rate of IFEs approximately trebled. And yet, in more recent observations with Venus Express, the occurrence of IFEs is now lower than the average we find outside this region."