The International Space Station orbits Earth. (Image by NASA)

The DART (Double Asteroid Redirection Test) mission, which was recently profiled in this column, has successfully launched on board a Falcon 9 rocket.

DART has begun a 10-month journey to impact an asteroid named Dimorphos. The first mission dedicated to planetary defense, DART will test the viability of the kinetic impactor asteroid redirection strategy. If we were to find an asteroid on an Earth-impacting path, we want to know what methods will best help us avoid catastrophe or extinction.

NASA has discovered and plotted the orbits of more than 26,000 near-Earth asteroids. Luckily, none of these asteroids is on a collision course with our planet, but the day may come when we discover one that is.

As real a threat as big rocks from space pose, it turns out to be tiny shards of human-made objects that pose the most immediate danger. On Nov. 15, a Russian anti-satellite missile struck and destroyed the defunct Kosmos-1408 satellite. The resulting debris field consists of over 1,500 pieces of former satellite travelling at more than 17,000 mph.

This cloud of debris is in an orbit similar to that of the International Space Station (ISS). The seven-member crew of the ISS had to take shelter in the Soyuz and Crew Dragon vehicles docked at the station during multiple passes of the debris field soon after the destruction of Kosmos-1408.

The Soyuz and Crew Dragon craft act as lifeboats, with all crew members ready to depart the station on a moment’s notice in case of catastrophic impact. Any piece of orbital debris measuring larger than 1 cm in diameter can breach the hull of the ISS. The resulting impact would hit like an explosive, causing pressure loss, attitude control loss, and extreme danger for any astronauts aboard.

Tests of this sort are unnecessary and create potential hazards for humans and satellites. NASA currently tracks over 27,000 pieces of orbital debris. There may be as many as half a million pieces of debris larger than 1 cm in diameter in low-Earth orbit.

It is possible that a catastrophic chain reaction, known as the Kessler syndrome, could result from an explosive event such as this anti-satellite test. A cascade of orbital collisions would create a debris swarm that could destroy our fleet of satellites and trap humanity on Earth for hundreds or thousands of years.

The Morning Sky

If you thought 17,000 mph was fast, how about 365,000 mph? That’s how fast the Parker Solar Probe was travelling when it whizzed by the sun on Nov. 21. The sun, which rises after 7:30 a.m. at this time of year, is nearing its furthest point south for the year, reaching the Winter Solstice on Dec. 21. High overhead in the morning hours is the constellation Leo, the lion. Look for a backward question mark that signifies the head of the lion, with a nearby right triangle serving as the tail of the mythical beast.

The Evening Sky

Venus, low in the southwest as night falls, leads a parade of planets toward the horizon. Draw a straight line from Venus, up through Saturn and on to Jupiter to help you visualize the orbital plane of the solar system. Known as the ecliptic plane, it traces the path of the Sun across the sky.

Dan Price is a NASA/JPL Solar System Ambassador and informal educator. He leads the Night Sky Tours at Josephine Sculpture Park. Have a question about astronomy or space science? Send an email to and it might be featured in a future column.

Recommended for you

Load comments

Thank you for reading!

Please log in, or sign up for a new account and purchase a subscription to read or post comments.