A lecture on the asteroid that led to dinosaur extinction and meteorite impacts on our earth in past and present was held Friday in the Kuiper Space Science building.

Part of the NASA Spacegrant, a funded statewide program enabling student research, the lecture was lead by David A. Kring, professor of planetary sciences.

Kring, who was part of the team that discovered the impact crater, said the theory was established when he and other scientists discovered an unusual rock layer in Colorado in the late 1980s.

"There are many theories about mass extinction, but this is the only one where you can find geological evidence," Kring said.

However, Kring said the impact itself did not kill off the dinosaurs. Instead, they became extinct from a four-day heat period during in which temperatures rose so high that dinosaurs actually passed out before forest fires started to spread over the world.

The rock contained iridium, which is mostly found in space and meteorites. This very thin layer did not come from Colorado, Kring said.

"The clue was iridium, which suggested that there was an impact somewhere in the world," said Kring.

Kring and the team, consisting of one UA undergraduate student and scientists from Mexico, took rock samples from around the world and found the thickest layer on Yucatan Peninsula in Mexico, where it was several meters high.

An impact crater covered with hundreds of feet of debris and 180 kilometers in diameter found at the site was proof that all iridium samples came from that single meteorite impact, Kring said.

The team called the crater "Chicxulub" which is Mayan for "tail of the devil." The team started drilling at the site in 2001, Kring said.

The asteroid was between 10 km and 17 km in diameter when it penetrated the Earth's surface up to 30 km deep at the impact, and vaporized parts of Earth's crust.

The impact threw out 25 trillion metric tons of debris and released toxic gases into the atmosphere, Kring said. Ten percent of the particles escaped gravity and emerged into space.

The carbon dioxide in the atmosphere increased by about 20 percent, but the sulfur aerosols from the fires, which block sunlight and let the earth cool off, increased by almost a million times.

Kring said in those conditions it would take approximately 10 years for the smoke and debris to settle.

"We have been busy finding the impact site, now we're in the position to ask harder questions, for example, how the ecosystem was affected. There's decades of more work to be done," Kring said.

Aside from the influence of crater impacts in relation to dinosaurs, the lecture also focused on craters in general and their affect on Earth today.

Kring said there are not many craters preserved on earth today because of its geological evolution. However, the moon shows impacts that can be compared to Earth, since the conditions at that time were essentially the same.

Meteorite impacts have decreased dramatically, but there has been a time when they were common. Earth has experienced about 40 impacts that left craters of more than 1,000 km in diameter, which destroyed everything that existed before.

"About 3.9 billion years ago the Earth and moon have been completely resurfaced, we have found nothing older that that on earth," Kring said.

Kring said those events could have resulted in the first signs of life on earth.

"Life may have been started there. The surface conditions weren't survivable, the survivable habitat was only in the subsurface hydrothermal conditions," Kring said.

When asked if asteroids could hit again, Kring replied, "It could happen tomorrow, and it will happen again. Small ones frequently, big ones less frequent, that's good for us."

However, Kring said even relatively small asteroids like the one that hit Northern Arizona about 50,000 years ago and was 150 feet in diameter, would flatten surroundings for several miles.

Heather Fauland, Near Eastern studies and economics junior and part of the NASA Spacegrant internship program, said she found the lecture interesting and easy to understand.

"I was able to understand what he was saying, even though I only know basics of geology. It was really interesting," Fauland said.

James Hoy, astronomy and physics senior, said he enjoyed the lecture because of his interest in crater impacts.

"I've learned a lot of geological stuff in class before, but I'm interested in the environmental effects of impact cratering," Hoy said. "(The lecture) was more detailed than in class, and I have learned some new stuff."