The Earth as viewed from a composite of NASA satellite images from space in the early 2000s. While it may seem like a tall order to end all human life on the planet from an external threat, the Universe is more than up to the challenge. (NASA / BLUE MARBLE PROJECT)

5 Killer Events From Space That Could Wipe Out Human Life On Earth

Even if we don’t destroy ourselves, we always have the Universe to contend with.

Ethan Siegel
Starts With A Bang!
3 min readMar 25, 2019

Wiping out all life on Earth is hard, but causing mass extinctions is easy.

The 1991 eruption of Mt. Pinatubo was the largest volcanic eruption to occur in our lifetimes. One that was perhaps 10,000 times the magnitude of this could threaten human life on Earth, and perhaps volcanism was the cause of at least one of our previous major mass extinctions. (ALBERT GARCIA)

Five major extinction events have occurred since the Cambrian explosion, each eradicating over 60% of terrestrial species.

A measure of biodiversity, and changes in the number of genera that exist at any given time, to identify the most major extinction events in the past 500 million years. They are not periodic, and only the most recent one (from 65 million years ago) has a known cause. (WIKIMEDIA COMMONS USER ALBERT MESTRE, WITH DATA FROM ROHDE, R.A., AND MULLER, R.A.)

At least five extraterrestrial scenarios are capable of wiping humanity out.

A large, rapidly moving mass that strikes the Earth would be certainly capable of causing a mass extinction event. However, such events appear to be relatively rare. Even though asteroid and comet strikes are frequent, one that causes a mass extinction may be rare enough that no such strikes will occur for billions of years. (DON DAVIS (WORK COMMISSIONED BY NASA))

1.) Asteroid/comet strike: a giant impact triggered the last great mass extinction 65 million years ago.

The comet that gives rise to the Perseid meteor shower, Comet Swift-Tuttle, was photographed during its last pass into the inner Solar System in 1992. The influence of the gravity of the other planets has the potential to dramatically change its orbit, however, making it a potential threat to Earth in the year 4479. It has been called the single most dangerous object known to humanity by NASA. (NASA)

Comet Swift-Tuttle, which could strike Earth in 4479, carries 28 times the destructive energy of that event.

This illustration of the most distant gamma-ray burst ever detected, GRB 090423, is thought to be typical of most fast gamma-ray bursts. When one or two objects violently form a black hole, such as from a neutron star merger, a brief burst of gamma rays followed by an infrared afterglow (when we’re lucky) allows us to learn more about these events. The gamma rays from this event lasted just 10 seconds, but Nial Tanvir and his team found an infrared afterglow using the UKIRT telescope just 20 minutes after the burst. (ESO/A. ROQUETTE)

2.) Gamma-ray burst: the brightest electromagnetic events of all are a once-per-million-years risk.

What we perceive as a gamma ray burst is now known to have at least one identified cause: in merging neutron stars. If one of the jets from these mergers is pointed at Earth, and is close enough (within about 6,000 light-years), it could destroy the ozone layer, which would lead to humanity’s demise. (NASA / JPL)

If one occurred within 6,000 light-years of Earth, it would destroy our ozone layer, causing a mass extinction.

70,000 years ago, a brown dwarf pair known as Scholz’s Star, right on the precipice of igniting hydrogen fusion in its core, passed through the Solar System’s Oort cloud. Stars, failed stars, and stellar remnants pass through our Solar System multiple times every million years. (JOSÉ A. PEÑAS/SINC)

3.) A random encounter: the galaxy is full of stars, planets, stellar remnants, and black holes.

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Ethan Siegel
Starts With A Bang!

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.