Chapter 1: The Cosmic Collision That Shocked Science

The story of a comet known as Shoemaker-Levy 9, which began its impact with Jupiter on July 16, 1994, is a thrilling chapter in astronomical history. Over the course of a week, this comet broke apart due to Jupiter's immense gravitational forces, creating 21 separate fragments. This remarkable event marked the first time scientists were able to observe an extraterrestrial collision live.

However, not everyone was thrilled. Just two days before the impacts, the journal Nature published a rather pessimistic article titled "The Big Fizzle Is Coming." It suggested that the impacts might be less impressive than anticipated, comparing them to a previous explosion over the South Pacific that yielded around 15–20 kilotons. The article downplayed the potential of Shoemaker-Levy 9, estimating its impacts at around 30 megatons each, significantly lower than the 100,000 megaton explosions some had predicted.

Despite the skeptics, the actual impacts were far more dramatic than anyone expected. The fragments struck Jupiter's southern hemisphere at speeds reaching 134,000 mph. One of these fragments, known as fragment G, was about 1.2 miles wide and produced an explosion equivalent to 6 million megatons, creating a massive hole in Jupiter’s atmosphere, roughly the size of Earth itself.

This event did more than silence the naysayers; it reignited the debate about the role of asteroids in mass extinction events, particularly regarding the dinosaurs. Previously, many paleontologists believed that the Cretaceous-Paleogene extinction event was a gradual process rather than a sudden catastrophe caused by an asteroid. However, the evidence from Shoemaker-Levy 9 suggested otherwise.

The asteroid that is believed to have led to the extinction of the dinosaurs was approximately 6.2 miles in diameter, creating a crater in Mexico that is 110 miles wide and 12 miles deep, wiping out around 75% of all life. Notably, this is only the second largest impact recorded on Earth, with the largest being the Vredefort impact structure in South Africa, thought to be between 6.2 and 9.3 miles wide.

While we can be confident about these known events, there are undoubtedly many impacts we are unaware of.

So, you might wonder, why does this matter?

NASA's Double Asteroid Redirection Test (DART) on September 26, 2022, successfully crashed a satellite into an asteroid to assess our capability to alter potentially hazardous asteroids. This is a crucial step toward establishing a planetary defense system.

So, let’s appreciate the fascinating nature of space rocks!

The first documented discovery of an asteroid occurred on January 1, 1801, at the Palermo Astronomical Observatory by Giuseppe Piazzi, who initially thought it was a planet. This discovery, named Ceres, was later reclassified as a dwarf planet by astronomer William Herschel, who recognized its smaller size.

Currently, there are approximately one million known asteroids, primarily located in the asteroid belt, which collectively possess about 3% of the Moon's mass. Notably, Ceres makes up 39% of this mass.

Asteroids come in various forms, and not all are rocky. Here's a quick rundown:

• An asteroid is a rocky body orbiting the Sun.
• A comet is a mixture of ice and dust that also orbits the Sun.
• A meteor is a space rock that has entered Earth's atmosphere.
• A meteorite is a meteor that has survived its atmospheric journey to land on Earth.

You may be pondering the potential risk of asteroids colliding with Earth. Generally, any rock smaller than 25 meters (about 82 feet) would likely disintegrate upon atmospheric entry. Larger asteroids can cause significant localized destruction. Smaller asteroids often pass near Earth unnoticed until they are detected later, and some may remain undetected entirely.

For example, we identified the asteroid 367943 Duende (98 feet across) a year ahead of its closest approach. However, just hours before it came near Earth, the Chelyabinsk meteor exploded over Russia without any prior warnings.

In fact, multiple meteor explosions have occurred in recent years, including one over Utah on August 13, 2022, and another over Mississippi on April 27, 2022. Even Ontario, Canada, experienced a meteor explosion on April 17, 2022.

When considering the destruction potential of small asteroids, it’s essential to note that their impact can be akin to a nuclear explosion, although without the radioactive fallout. Factors such as the asteroid's density, the target's composition, and the angle of approach will all influence the impact's severity.

Asteroid impacts can unleash immense energy, with the potential to cause widespread destruction. However, thankfully, a catastrophic asteroid impact does not appear to be imminent. For instance, the asteroid 1950 DA is predicted to come close to Earth around the year 2880.

Though I may not possess formal qualifications, I confidently assert that a significant asteroid collision is unlikely in the near future. If one were to occur, we would likely have some warning, albeit possibly not enough time to enact a sufficient response.

The real concern lies not in world-ending impacts but rather in smaller ones that could devastate cities.

Space is vast, and monitoring it continuously is a daunting task.

Bill Bryson discusses in his book, A Short History of Nearly Everything, what would transpire if a massive asteroid, like the one responsible for the Manson crater, were to strike Earth today.

Upon entering the atmosphere, the asteroid would generate extreme heat, vaporizing anything in the immediate area. Seconds later, the impact would send debris soaring into the atmosphere, obliterating everything within a 150-mile radius and creating a shockwave traveling at nearly the speed of light.

The devastation would extend far beyond the initial impact site, with superheated rocks raining down, disrupted communications, potential volcanic eruptions, and earthquakes worldwide. The initial day could witness the loss of at least a billion lives, drastically affecting Earth’s ability to sustain life.

Let’s hope that if such a disaster were to occur, it happens on a Monday—right?

You take care out there!

For further reading, most sources are linked throughout the text. For additional context regarding the asteroid impact scenario discussed, I consulted:

Bryson, Bill. A Short History of Nearly Everything. Black Swan, 2016.

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Chapter 2: Understanding Asteroid Impacts

The first video, titled "GET YOUR BUTT OUTTA HERE! (2-12-14)," humorously delves into the reactions surrounding asteroid collisions and their significance.

The second video, "SUPER PU