that an asteroid that large would have created a layer of dust that would have surrounded the Earth, lowering temperatures and causing deadly, highly acidic, rain.
Will another large asteroid strike the Earth?
Yes, asteroids have struck the Earth in the past and are likely to strike again in the future. Small asteroids strike the planet about every 1,000 to 200,000 years. Large asteroids are much less likely to threaten the planet; they strike only about three times every million years. Huge asteroids, such as the one that may have killed dinosaur species, are even less frequent.
How many places on Earth have evidence of asteroid impacts?
There are about 160 places on Earth that display evidence of asteroid impacts. Depending on the size of an asteroid, it can have significant effects on the planet. If an asteroid strikes the ocean, it can create huge, destructive tsunamis or tidal waves. If an asteroid strikes land, it can create a huge crater, cause earthquakes, and propel debris into the atmosphere, creating major climatic changes.
What is a Potentially Hazardous Asteroid (PHA)?
A PHA is an object that is 3.28 feet (1 meter) in length, which is large enough to be detected by astronomers on Earth. It has an orbital path that could bring it in close proximity to Earth. It is very hard to predict the orbital path of a PHA, since its trajectory is always influenced by its proximity to a nearby planet’s gravitational pull.
How much junk is orbiting our planet?
According to scientists at NASA who track orbital debris, there are approximately 500,000 pieces traveling around the Earth, some at speeds of up to 17,500 miles per hour, from tiny screws to booster rockets. Of the 500,000 pieces, more than 20,000 pieces are larger than a softball. Some are as small as flecks of paint, which may damage orbiting spacecraft like the International Space Station, because of their speed. NASA, the U.S. Department of Defense, and other space agencies are able to track about 21,000 pieces of debris.
There are essentially two levels of space junk around our planet: objects in geosynchronous orbit and those in low Earth orbit.
How many Potentially Hazardous Asteroids is NASA tracking that could impact the Earth in the twenty-first century?
There are approximately 1,572 PHAs that are on NASA’s list of most likely objects whose orbital paths may bring them close to the Earth’s orbit sometime in the next 100 to 200 years. Scientists have not fully calculated the risks because they still need to figure out the effects of gravity of various planetary bodies on the exact course of the asteroids. At best, scientists may calculate the probability of a collision with Earth, during a certain period of time.
What is a Near Earth Object (NEO)?
A Near Earth Object is any object in space that is relatively close to Earth and is of any size. The difference between an NEO and a Potentially Hazardous Asteroid (PHA) is that PHAs are anything larger than 500 feet (150 meters) in diameter and have orbits that bring them closer than 4,650,000 miles (7,480,000 km) to Earth. All PHAs are also NEOs, but not all NEOs are PHAs.
How many Near Earth Objects is NASA tracking?
Since the first Near Earth Object was discovered in 1973, approximately 12,000 objects are currently being tracked by NASA.
When and where was the last great impact on the Earth from a Near Earth Object?
The last big impact was in June of 1908 in Tunguska, Russia, in Siberia. Scientists do not know for sure what hit the Earth, as it could have been a comet or asteroid. But whatever it was, it had an estimated explosive energy of fifteen megatons. The impact event is significant because it was the first time during the modern era that we had eyewitness accounts by locals living nearby. The object is estimated to have been 120 feet (36.58 meters) wide and traveled at a speed of 33,500 miles per hour (53,913 km/hr).
What is the Space Guard Survey?
The Space Guard Survey refers to many initiatives by organizations such as NASA to catalogue all Near Earth Objects that are larger than 0.6 miles (1 kilometer) in diameter. The survey assesses their potential intersection with Earth’s orbital path to determine if they are a threat.
How much of the Earth is covered by water?
About 71% of the surface area of the Earth is covered by water. Oceans hold 96.5% of the Earth’s water. The other 29% of the Earth is land, located primarily in the Northern Hemisphere. If you look at a globe, you’ll notice that the Southern Hemisphere has a much larger surface area covered with water.
How much is the sea level rising?
Scientists believe that sea levels are rising by approximately .12 inches (3.05 mm) per year. The rising sea levels have been more extreme during the past century because of the increase in temperature of the world’s oceans as well as the gradual melting of ice in the Earth’s polar regions. The recent increase in sea levels are more extreme than over the past one thousand years.
What countries are threatened the most from rising sea levels and may cease to exist in the twenty-first century?
Many of the world’s small island nations are concerned about the rising sea levels. Lowlying island nations of the Pacific and Indian oceans are most at risk, most notably Tuvalu, the Maldives, Palau, and Micronesia. Other candidates for severe flooding and reclamation of coastal land by the impending sea include Bangladesh, India, Thailand, Vietnam, Indonesia, and China, affecting the lives of hundreds of millions of people.
How much land disappears when the sea level rises?
Scientists believe that as the seawater rises by 0.04 inches (1 millimeter), the shoreline disappears by 4.9 feet (1.5 meters). This means that if the sea level rises by 3.28 feet (1 meter), the shorelines will extend another 1 mile (1.6 km) inland.
What is a nautical mile?
Used for measuring ocean-based distances, a nautical mile is equivalent to approximately 6,076 feet (1,852 meters) or 1.15 miles (1.85 km). The speed of ships is measured in knots. One knot is equivalent to one nautical mile per hour.
What is the average depth of the Earth’s oceans?
The average depth of the Earth’s oceans is approximately 14,000 feet (4,267.2 meters) deep.
What percentage of the Earth’s surface is covered by water?
Approximately 70.8% of the Earth’s surface is covered by saltwater. Although we have but one giant, interconnected ocean covering the planet, we divide it into large sections called oceans and smaller bodies of water called seas.
How is water distributed on the Earth?
The oceans contain approximately 97% of all of the world’s water. Of this ocean water, 96% is saltwater or saline. The other 4% is comprised of freshwater flows, ice, snow, and precipitation. Of the 3% of nonocean water, approximately 69% of that is frozen in the form of glaciers and ice caps; 90% of this water is in Antarctica, and about 9% is in Greenland. What
