A small white bag that has been to the moon and back — both literally and metaphorically — was purchased by an anonymous buyer for $1,812,500 (including a premium of $312,500) at auction at Sotheby’s on Thursday.

The bag, which still contains particles of moon dust, was used to collect samples of lunar rocks by Neil Armstrong in 1969. Sotheby’s did not identify the person who bought the bag on Thursday, except to say that the buyer or buyers are American.

The sale was part of a special auction of 173 items related to space exploration, including photographs, artifacts and models of spacecraft. The event was timed for the 48th anniversary of the day Mr. Armstrong and Buzz Aldrin first touched down on our lunar satellite.