Quiz of the Day
Asteroids & Space Threats
Tuesday, 30 June 2026
Asteroid Day — near-Earth objects, the Tunguska event, planetary defence and cosmic close calls
1. What event does Asteroid Day (30 June) specifically commemorate?
- The discovery of the asteroid belt
- The Chicxulub impact that killed the dinosaurs
- The first asteroid mining proposal
- The Tunguska explosion of 1908
On 30 June 1908, a massive explosion flattened about 2,150 square kilometres of Siberian forest — an area roughly the size of Greater London. The blast was equivalent to 10-15 megatons of TNT, about 1,000 times more powerful than the Hiroshima bomb.
2. What is a 'near-Earth object' (NEO)?
- A satellite in low Earth orbit
- A star within 10 light-years of Earth
- Any object within the solar system
- An asteroid or comet whose orbit brings it within 1.3 AU of the Sun
As of the mid-2020s, over 34,000 near-Earth objects have been discovered. About 2,400 of these are classified as 'potentially hazardous' — meaning they are larger than 140 metres and pass within 7.5 million km of Earth's orbit.
3. What was the name of NASA's 2022 mission that deliberately crashed a spacecraft into an asteroid to test planetary defence?
- New Horizons
- OSIRIS-REx
- Deep Impact
- DART
The Double Asteroid Redirection Test (DART) hit the asteroid moonlet Dimorphos at 22,530 km/h on 26 September 2022. It successfully changed Dimorphos's orbital period by 33 minutes — far exceeding the minimum goal of 73 seconds. It was humanity's first planetary defence test.
4. Which asteroid impact is believed to have caused the extinction of the dinosaurs about 66 million years ago?
- The Tunguska impactor
- The Vredefort impactor
- The Chicxulub impactor
- The Barringer impactor
The Chicxulub asteroid was roughly 10-15 km wide and hit what is now Mexico's Yucatan Peninsula. The impact released energy equivalent to 72 trillion tons of TNT, triggered mega-tsunamis, global wildfires, and a 'nuclear winter' that blocked sunlight for years.
5. How fast do most asteroids travel relative to Earth when they pass nearby?
- About 25,000 to 72,000 km/h
- About 10,000 km/h
- About 200,000 km/h
- About 1,000 km/h
At these speeds, even a small asteroid carries enormous kinetic energy. A 20-metre asteroid entering the atmosphere releases energy equivalent to a small nuclear weapon. The 2013 Chelyabinsk meteor entered at about 66,000 km/h.
6. What happened over the Russian city of Chelyabinsk on 15 February 2013?
- A satellite crashed to Earth
- A total solar eclipse
- A meteorite landed in a school playground
- A 20-metre asteroid exploded in the atmosphere
The Chelyabinsk meteor exploded with the force of about 500 kilotons of TNT at an altitude of 30 km. The shockwave injured over 1,500 people, mostly from shattered glass. No one saw it coming because it approached from the direction of the Sun.
7. What is the largest known asteroid in our solar system?
- Eros
- Vesta
- Pallas
- Ceres
Ceres is so large (940 km diameter) that it was reclassified as a dwarf planet in 2006 — the same year Pluto was demoted. NASA's Dawn spacecraft orbited Ceres from 2015 to 2018 and discovered mysterious bright spots that turned out to be salt deposits from subsurface brine.
8. What scale measures the risk of an asteroid impacting Earth?
- The Saffir-Simpson scale
- The Torino scale
- The Richter scale
- The Mohs scale
The Torino scale runs from 0 (no hazard) to 10 (certain collision capable of causing global catastrophe). It was adopted in 1999 at a conference in Turin (Torino), Italy. No asteroid has ever been rated above 4 on the scale, and those ratings were later downgraded to 0.
9. Approximately how often does a Chicxulub-sized asteroid (10+ km) impact Earth?
- Every 100 million years
- Every 1 million years
- Every 1,000 years
- Every 1 billion years
While catastrophic impacts are extremely rare, smaller but still devastating impacts occur more frequently. A Tunguska-sized event (capable of destroying a city) happens roughly every 500-1,000 years. Most go unnoticed because they occur over oceans or uninhabited areas.
10. What is the name of the asteroid from which NASA's OSIRIS-REx mission collected a sample, returned to Earth in 2023?
- Ryugu
- Itokawa
- Apophis
- Bennu
OSIRIS-REx collected about 121 grams of material from Bennu's surface and returned it to Earth on 24 September 2023. Early analysis revealed the sample contained water, carbon molecules, and amino acids — ingredients that may have helped seed life on Earth.
11. Which asteroid will pass very close to Earth in 2029, close enough to be visible to the naked eye?
- Apophis
- Toutatis
- Eros
- Bennu
Asteroid Apophis (named after the Egyptian god of chaos) will pass within about 31,000 km of Earth on 13 April 2029 — closer than geostationary satellites. It is about 370 metres wide. When discovered in 2004, it briefly had a 2.7% probability of hitting Earth in 2029.
12. What is the asteroid belt located between?
- Earth and Mars
- Neptune and Pluto
- Jupiter and Saturn
- Mars and Jupiter
Despite movie depictions, the asteroid belt is mostly empty space. If you combined all the asteroids in the belt, they would form an object smaller than Earth's Moon. The average distance between asteroids is about 1 million km — spacecraft pass through routinely without incident.
13. What is the Barringer Crater in Arizona also known as?
- Meteor Crater
- Arizona Impact Basin
- Grand Crater
- Death Valley Crater
Meteor Crater is about 1.2 km wide and 170 metres deep, formed roughly 50,000 years ago by a nickel-iron meteorite about 50 metres across. The energy released was equivalent to 10 megatons of TNT. NASA astronauts trained there before the Moon missions.
14. What does the ESA's planned Hera mission aim to study?
- A comet heading towards Earth
- The asteroid belt between Mars and Jupiter
- The surface of Mars
- The aftermath of the DART impact on Dimorphos
Hera launched in October 2024 and will arrive at the Didymos-Dimorphos system in 2026 to conduct a detailed post-impact survey. It will measure the crater left by DART and determine exactly how much Dimorphos's mass and shape changed — critical data for future planetary defence.
15. What would happen if a 1-km asteroid hit the ocean?
- Nothing significant — it would just sink
- It would evaporate the ocean entirely
- It would create a new island
- It would create mega-tsunamis hundreds of metres high
A 1 km asteroid hitting the ocean at typical speeds would blast a temporary crater in the water up to 20 km across. The resulting tsunamis could reach hundreds of metres in height near the impact and devastate coastlines thousands of kilometres away. Dust and water vapour would also cause global climate disruption.