Arizona asteroid explosion

The explosion of a small asteroid over Arizona in the early hours of 2 June is a timely reminder of the unseen and sometimes unpredicable threat facing our planet.

The asteroid hit Earth's atmosphere at around 4 am local time and the airburst cause by its explosion shook the ground below and produced a flash of light 10 times  brighter than a full Moon. NASA described as a three metre wide space rock that originated from beyond the orbit of Mars.

Shortly after the explosion, Mike Lerch walked out the front door of his house in Phoenix on the way to work. "At first I thought it was a rocket launch," he says. "Now I realise it was debris from the asteroid."

The smoke trail remains shown clearly in his picture below were widely visible as they twisted in the winds high above Arizona.

Bill Cooke of NASA's Meteoroid Environment Office says this is the brightest fireball detected in the eight-year history of NASA's All Sky Fireball Network, an array of cameras that monitors fireball activity across the USA.

The flash itself was so bright, it briefly turned night into day, graphically illustrated in these before, during, and after shots captured by one of the NASA cameras in Sedona, Arizona. The camera was facing NE so it did not record the asteroid itself.

The fact that the explosion blinded most cameras that saw it initially complicated analysts' efforts to pinpoint the asteroid’s nature and origin. Ultimately, however, they were able to draw firm conclusions - the mass of the asteroid was some tens of tons and it exploded with a kinetic energy of approximately 10 kilotons.

"There are no reports of any damage or injuries -just a lot of light and few sonic booms," says Cooke. "If Doppler radar is any indication, there are almost certainly meteorites scattered on the ground north of Tucson.”

Dangers posed by asteroids impacting Earth was one of the topics discussed at the 4th Manfred Lachs International Conference on Conflicts in Space and the Rule of Law held in Montreal, Canada, the weekend before.

Comets and asteroids colliding with Earth pose a serious threat to humanity yet we lack effective means to discover them and alert the public to imminent dangers. Even the impact of a small celestial body may lead to serious loss of life, significant material and ecological damage.

For more information see 'Protecting Earth from cosmic disasters' in the spring 2016 edition of 'ROOM - The Space Journal'.