Look for the ‘fireworks moon’ this Independence Day

Posted July 1, 2012

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 Fourth 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).

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 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 (http://bbc.in/Lg0VZa ) or LHB.

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.

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 estimated 19-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.

King is photo editor at the Duluth New Tribune and an amateur astronomer who blogs at astrobob.areavoices.com

Tags: news, fireworks, moon