“Fireworks Moon” Sure To Delight This 4th Of July

Fireworks at Fourth Fest at Bayfront Park in Duluth in 2010. This year the nearly full moon will share the scene. Photo: Bob King

No auroras around here last night though I suspect there would have been a green glow in the north were it not for moonlight. There’s still a chance for magnetic storms and potentially more auroras this evening through July 3. Take a minute to scan the northern sky before going to bed the next few nights just in case.

The kids in my township love setting off firecrackers and bottle rockets well before the 4th of July. Last night a large explosion echoed loudly through the neighborhood under a tranquil moon and the silent strutting of fireflies. Thanks for the reminder guys (they’re always guys).

Simulated view looking southeast around 9:45 p.m. July 4. For the exact moonrise time for your town, click the photo. Remember to add an hour for daylight saving time to the times shown. Illustration: Bob King

This July 4 will be special because it happens just one day past full moon. While you relax on a blanket or get comfy in that lawn chair, the big orange eye of the moon will rise in the east around 9:30 p.m. local time about the time many cities start their fireworks shows. Bangs and showers of colored fire will rivet your attention, but the grand finale of it all may be the quiet moon taking center stage in the east.

If you have kids (or even if you don’t), use the  opportunity to point out the face of the “man in the moon”, explaining that the lighter-colored areas were once molten lunar crust that was later bombarded by meteorites, leaving it riddled with millions of craters like Swiss cheese on steroids.

The light-colored areas are ancient, now-solidified lunar crust. The dark spots are named “seas” because of their smoother appearance. Seas are named after moods and weather. Illustration: Bob King

The dark patches that form the eyes, nose and mouth are really huge holes blasted out by asteroids more than 3 billion years ago that later filled with dark-colored lavas.

The moon’s pretty quiet now, except for the occasional moonquake or meteorite hit, but the fireworks of bombardment during its youth was a grand finale that lasted some 300 million years. Scientists term the period of intense cratering that affected not only the moon but Earth, Mars and Venus, the Late Heavy Bombardment or LHB.

The reshuffling of the outer giant planets flung millions of comets and asteroids into the inner solar system bombarding the moon, Earth, Venus and Mars. Credit and copyright: Julian Baum

The LHB occurred 4.1-3.8 billion years ago (some say 4.1 to 2.5 billion) 700 million years after the planets had formed. Jupiter, Saturn, Uranus and Neptune were rapidly migrating at that time to different positions in the outer solar system. Their movements stirred up millions of comets and asteroids, sending them into the inner solar system to wreak havoc on the rocky planets and their moons. Once the giants reached stable orbits, the neighborhood became a calmer place, and the moon was left with enough scars to arouse the curiosity of humans who would evolve several billion years later.

A team of scientists estimates that 3 billion years ago a small asteroid slammed into what is now Greenland to gouge the oldest crater found to date on Earth. Credit: Carsten Egestal Thuesen / GEUS

Earth also took its hits during the LHB. Just this week a team of scientists from Cardiff, the Geological Survey of Denmark and Greenland, Lund University in Sweden and the Institute of Planetary Science in Moscow announced the discovery of the oldest impact crater yet found on Earth – a 3-billion year old giant near the town of Maniitsoq in southwestern Greenland.

While the crater bowl has long since been eroded, scientists found evidence of shocked rocks, pulverized granite and deposits of nickel and platinum, elements often found in meteorites. The estimated19-mile-wide asteroid blasted out a crater that was originally 373 miles across and over 15 miles deep. After billions of years of erosion, only a 62-mile-wide remnant survives.

Space rocks still fling about the sun creating concerns for the future, but it’s nothing compared to the LHB. While you’re out watching things blow up on the 4th, let your imagination wander to those earlier days when the fireworks never seemed to end.

2 Responses

  1. andrew

    Astrology is a great subject.I like astrology and space science.I read something like parallel universe and i am trying myself to understand about space science. From the ageof 13 ,i research about parallel science.

    1. astrobob

      Hi Andrew,
      I think you mean “astronomy”. Glad to hear you enjoy studying parallel universes – food for the imagination!

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