Discover more from Learning by Proxy with Vivek Srinivasan
Moving a World
We now wield the power of the gods.
On the Yucatan Peninsula in Mexico is located the Chicxulub Crater. The crater measures 180 kilometres in width and is 20 km deep. It is estimated that the impactor asteroid would have been 10 km in diameter. The asteroid that landed in this crater is considered the dinosaur killer.
The earth is visited by several asteroids every night and they vaporise in the upper atmosphere. Most are harmlessly small. Some of them turn out to be significant. The really large ones may not even burn out till they reach the surface. Earth has not been visited by extinction-level asteroids very often because of Jupiter, whose immense gravity draws many of them in. Further, we have our moon which takes a lot of beating as well as evidenced by the number of craters on it.
A piece of rock coming from outside our system must pass the gravitational pull of the four gas giants - Neptune, Uranus Saturn and Jupiter, then miss Mars and the moon to strike us. This has protected us during our 300,000-year journey as a species, but the next big asteroid might be just around the corner.
On cosmic scales, 10 Kms is not a very large object. It would be easy to miss it despite all of the telescopes that we have pointed at the night sky.
You may have watched movies like Armageddon and Deep Impact where asteroids are headed for Earth and the greatest minds have to come up with a plan - Fast.
That no longer remains true.
In 2015, the European Space Agency (ESA) and NASA devised a plan to launch a satellite that would redirect a small asteroid. The mission got the name Double Asteroid Redirection Test (DART) for short. The idea was to hit an asteroid with a payload and see if we could move it. In the case of DART that payload was 610 Kgs. The target was an asteroid called Dimorphos which is part of the Didymos system, a binary asteroid system (one asteroid orbiting the other) much like the moon orbits the Earth.
This was not the first time NASA was about to crash something on a heavenly body.
Deep Impact is a NASA space probe launched from Cape Canaveral Air Force Station on January 12, 2005. It was designed to study the interior composition of the comet Tempel 1 (9P/Tempel), by releasing an impactor into the comet. At 05:52 UTC on July 4, 2005, the Impactor successfully collided with the comet's nucleus. The impact excavated debris from the interior of the nucleus, forming an impact crater. Photographs taken by the spacecraft showed the comet to be more dusty and less icy than had been expected. The impact generated an unexpectedly large and bright dust cloud, obscuring the view of the impact crater.
DART took off in November 2021 to crash into the asteroid. Two weeks ago on 26th September 2022, the craft crashed into the asteroid. These were the last pictures relayed to us by the craft.
Dimorphos orbits another asteroid. The only way to know if the mission has succeeded was by measuring the time it takes to orbit. Each time that it passes around its sister asteroid, the light from the system dims. By measuring how long that takes, scientists can figure out the change.
The results came in.
The space agency and its partners planned that collision to see whether such an impact could alter an asteroid or comet’s trajectory—should humanity ever need to defend the planet from an oncoming space rock. Before the crash on September 26, Dimorphos circled its neighbor like clockwork: one lap every 11 hours and 55 minutes. If the DART test was successful, the proof would be a change in that orbital period, showing that the refrigerator-sized spacecraft had nudged the asteroid onto a different path.
Now the DART team has an answer: It worked—even better than expected. “For the first time ever, humanity has changed the orbit of a planetary body,” said Lori Glaze, director of the Planetary Science Division at NASA headquarters in Washington, at a press conference today revealing the result.
The team would have considered a 10-minute difference a success, said NASA chief Bill Nelson. But DART actually shortened the asteroid’s orbit by a whopping 32 minutes. Dimorphos now takes only about 11 hours and 23 minutes to circle its partner, he said—a significant change, meaning that it is indeed possible to deflect a small asteroid’s path. “NASA is serious about defending the planet,” he said.
By asteroid standards, Dimorphos is very small. Measuring 208 m X 160 m X 133 m it is the size of the pyramid of Giza. If it was bound for Earth, it would certainly burn up in the upper atmosphere. With a diameter of about 170 m, it is a little less than two football fields in size.
It is 1/60th the size of the asteroid that created the Chicxulub Crater.
Earth has a moon. What if it did not?
So, wiping out the Moon would certainly have some good, bad and ugly consequences straight away, but hardly apocalyptic. The biggest impact would take time to manifest: destabilising the Earth’s rotation. Today, Earth’s axis is tilted at 23.4° with respect to our orbit around the Sun. But there is a slight wobble in this spin cycle. The wobble is like the one you see with a spinning top, slowly making the tip trace a circle as the toy spins rapidly around. For the Earth, it’s a rather slow wobble, taking around 26,000 years to go full circle. It’s also quite gentle, moving the Earth’s axis by just 2.4 degrees. But without the Moon to stabilise it, this wobble would become erratic and extreme.
Sometimes, the Earth’s axis would point straight up and down at right angles to the Earth’s orbit of the Sun. In this scenario, seasons would be a thing of the past, and night and day would be equally long all year round. At other times, the Earth would tilt all the way over and lie on its side in relation to its orbit around the Sun. This would mean the poles would be burning hot and the equator freezing cold.
In effect, removing the Moon would spell extreme climate change. There would be huge differences between temperatures and daylight throughout the year, and ice ages would hit different parts of the world every few thousand years. Lucky for us then that the Moon is going nowhere any time soon.
Source: Institute of Physics
This is a small step but a monumental achievement. This is the first time humans have been able to change the way another body moves in the cosmos. The degree to which we are in a position to affect the universe cannot be understated. We knocked the moon of an asteroid and affected its orbit. Imagine what else we could do. Imagine knocking out the moon of an inhabited planet!
We have engaged in the wanton destruction of this planet for money. Something that is not even real! We are an ultimately irresponsible species.
With great power comes great responsibility. Who is taking responsibility?