This gorgeous photo of the Moon was taken by the astronauts of Apollo 8. Two of the Moon's most recognizable craters are clearly visible: The dark-floored crater in the lower right is the Lomonosov crater, measuring about 80 kilometers (50 miles) in diameter. The bright-rayed crater is Giordano Bruno, about 21 kilometers (13 miles) in diameter.

Photograph courtesy NASA

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  • On June 18, 1178, five monks in Canterbury, England, may have witnessed the formation of a crater on the Moon. The crater, marked by a bright ray system, is today known as the Giordano Bruno crater.
    The monks reported an impact in which “the upper horn [of the moon] split in two” and a “flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals and sparks.” 
    Modern astronomers say the monks’ account might actually be pretty accurate! A passing comet or asteroid probably collided with the Moon. The collision likely caused impact melts, or rocks melted by the shock of the powerful impact. This molten material could be the “flaming torch” the monks described.
    Many modern astronomers, however, don’t think the crater is quite so young, and they’re not sure what the monks saw. According to NASA, one team calculated the age of Giordano Bruno by counting the number of craters that formed on the crater after its own formation. These scientists discovered Giordano Bruno is just over a million years old—very young by cosmic standards, but nowhere near young enough for the English monks to witness!
  • Term Part of Speech Definition Encyclopedic Entry
    accurate Adjective


    asteroid Noun

    irregularly shaped planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.

    astronomer Noun

    person who studies space and the universe beyond Earth's atmosphere.

    calculate Verb

    to reach a conclusion by mathematical or logical methods.

    collide Verb

    to crash into.

    comet Noun

    celestial object made up of ice, gas, and dust that orbits the sun and leaves a tail of debris.

    cosmic Adjective

    having to do with the universe (cosmos).

    crater Noun

    bowl-shaped depression formed by a volcanic eruption or impact of a meteorite.

    Encyclopedic Entry: crater
    impact Noun

    collision or crash.

    impact melt Noun

    rocks melted by the shock of a large impact, such as a meteorite on a planet.

    molten Adjective

    solid material turned to liquid by heat.

    monk Noun

    person who has withdrawn from everyday society and lives in service to a religious order.

    Moon Noun

    Earth's only natural satellite.

    NASA Noun

    (National Aeronautics and Space Administration) the U.S. space agency, whose mission statement is "To reach for new heights and reveal the unknown so that what we do and learn will benefit all humankind."

    ray system Noun

    radial streaks of fine ejected material thrown out during the formation of an impact crater.

    rock Noun

    natural substance composed of solid mineral matter.

    spew Verb

    to eject or discharge violently.

    witness Verb

    to see and be aware of by personal, first-hand knowledge.