K-T Boundary

Chicxulub Crater

What killed the dinosaurs? That’s a question that has puzzled paleontologists since dinosaurs were first discovered. Maybe the global climate changed, maybe they were killed by disease, volcanoes, or the rise of mammals. But in the last few decades, a new theory has arisen; an asteroid strike millions of years ago drastically changed the Earth’s environment. It was this event that pushed the dinosaurs over the edge into extinction. What’s the evidence for this asteroid impact? A thin dark line found in layers of sediment around the world; evidence that something devastating happened to the planet 65 million years ago. This line is known as the K-T boundary.

What is the K-T boundary? K is actually the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period. So the K-T boundary is the point in between the Cretaceous and Tertiary periods. Geologists have dated this period to about 65.5 million years ago.

When physicist Luis Alvarez and geologist Walter Alvarez studied the K-T boundary around the world, they found that it had a much higher concentration of iridium than normal – between 30-130 times the amount of iridium you would expect. Iridium is rare on Earth because it sank down into the center of the planet as it formed, but iridium can still be found in large concentrations in asteroids. When they compared the concentrations of iridium in the K-T boundary, they found it matched the levels found in meteorites.

The researchers were even able to estimate what kind of asteroid must have impacted the Earth 65.5 million years ago to throw up such a consistent layer of debris around the entire planet. They estimated that the impactor must have been about 10 km in diameter, and release the energy equivalent of 100 trillion tons of TNT.

When that asteroid struck the Earth 65.5 million years ago, it destroyed a region thousands of kilometers across, but also threw up a dust cloud that obscured sunlight for years. That blocked photosynthesis in plants – the base of the food chain – and eventually starved out the dinosaurs.

Researchers now think that the asteroid strike that created the K-T boundary was probably the Chicxulub Crater. This is a massive impact crater buried under Chicxulub on the coast of Yucatan, Mexico. The crater measures 180 kilometers across, and occurred about 65 million years ago.

Geologists aren’t completely in agreement about the connection between the Chicxulub impact and the extinction of the dinosaurs. Some believe that other catastrophic events might have helped push the dinosaurs over the edge, such as massive volcanism, or a series of impact events.

We have written many articles about the K-T boundary for Universe Today. Here’s an article about how the dinosaurs probably weren’t wiped out by a single asteroid, and here’s an article about how asteroids and volcanoes might have done the trick.

Here’s more information from the USGS, and an article from NASA.

We have recorded an episode of Astronomy Cast all about asteroid impacts. Listen to it here: Episode 29: Asteroids Make Bad Neighbors.


NASA Doesn’t Receive Enough Money for Mandated Asteroid Search

Planet Killer
Artist's conception of an asteroid hitting Earth.

In 2005, the US Congress mandated that NASA discover 90 percent of all near-Earth objects 140 meters in diameter or greater by 2020. But they forgot one minor detail: Congress or the administration did not request or appropriate any new funds to meet this objective, and with NASA’s existing budget, there is no way NASA can meet the mandated goal.

Does anyone else see a pattern here?

“For the first time, humanity has the capacity and the audacity to avoid a natural disaster,” says Irwin Shapiro of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who headed a National Research Council panel to asses NASA’s progress in reaching the asteroid detection goal . “It really is a question of how much to invest in an insurance policy for the planet.”

NASA was also directed by the Bush administration to build spacecraft to return to the Moon, and perhaps go on to Mars, but do the job (as well as complete the space station and make sure the shuttles can fly safely) with no real increase in budget.

From the report:

Currently, the U.S. government spends a relatively small amount of money funding a search and survey program to discover and track near-Earth objects, and virtually no money on studying methods of mitigating the hazards posed by such objects. Although Congress has mandated that NASA conduct this survey program and has established goals for the program, neither Congress nor the administration has sought to fund it with new appropriations. As a result, NASA has supported this activity by taking funds from other programs, while still leaving a substantial gap between the goals established by Congress and the funds needed to achieve them.

The report is available here (download the free pdf version)

But in summary, the report says that since only limited facilities are currently involved in the asteroid survey/discovery effort, NASA cannot meet the goals of the Congressional mandate on the existing budget. Instead, the three current survey efforts dedicated to the problem, supported at current levels, will likely find only about 15%.

The report also says that Harvard-Smithsonian’s Minor Planet Center is more than capable of handling the observations of the congressionally mandated survey, but there isn’t enough funds for adequate staffing.

If this is true, the facilities to do the job appear to be in place, and no new observatories need to be built or spacecraft need to be launched. How much more money would it take to hire enough people?

However, only three surveys are currently involved in the search (Catalina Sky Survey, Spacewatch and Lincoln Near Earth Asteroid Research), and the panel suggests that more telescopes and spacecraft would be beneficial to the search. Several ground-based telescopes have been proposed or are currently under development that could contribute substantially to meeting the goal established by Congress. However, none has yet been fully funded, nor principally dedicated to the NEO discovery goal.

Right now, the US is the only country that currently has an operating survey/detection program for discovering near-Earth objects. Canada and Germany are both building spacecraft that may contribute to the discovery of near-Earth objects, but neither mission will detect fainter or smaller objects than ground-based telescopes.

But the US isn’t alone in the non-funding of asteroid searches. “Virtually no international funds are spent supporting ground-based NEO surveys, and international NEO discovery efforts are largely conducted on an ad hoc, voluntary, or amateur basis. NASA is the agency that has funded more than 97 percent of the discoveries of NEOs in the last decade,” says the report.

Sources: USA Today, National Acadamies Press

Near-Earth Object Has Two Moons

Radar imaging at NASA's Goldstone Solar System Radar on June 12 and 14, 2009, revealed that near-Earth asteroid 1994 CC is a triple system. Image Credit: NASA/JPL/GSSR

Radar images have shown that a near-Earth object is actually a triple system; an asteroid with two small moons. NASA’s Goldstone Solar System Radar on June 12 and 14, 2009, revealed the new informaton about Asteroid 1994 CC. It came within 2.52 million kilometers (1.56 million miles) on June 10. Prior to the flyby, very little was known about this celestial body. 1994 CC is only the second triple system known in the near-Earth population. A team led by Marina Brozovic and Lance Benner, both scientists at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., made the discovery.

Asteroid 1994 CC encountered Earth within 2.52 million kilometers (1.56 million miles) on June 10. Prior to the flyby, very little was known about this celestial body. Image Credit: NASA/JPL/GSSR
Asteroid 1994 CC encountered Earth within 2.52 million kilometers (1.56 million miles) on June 10. Prior to the flyby, very little was known about this celestial body. Image Credit: NASA/JPL/GSSR

1994 CC consists of a central object about 700 meters (2,300 feet) in diameter that has two smaller moons revolving around it. Preliminary analysis suggests that the two small satellites are at least 50 meters (164 feet) in diameter. Radar observations at Arecibo Observatory in Puerto Rico, led by the center’s director Mike Nolan, also detected all three objects, and the combined observations from Goldstone and Arecibo will be utilized by JPL scientists and their colleagues to study 1994 CC’s orbital and physical properties.

The next comparable Earth flyby for asteroid 1994 CC will occur in the year 2074 when the space rock trio flies past Earth at a distance of two-and-a-half million kilometers (1.6 million miles).

Of the hundreds of near-Earth asteroids observed by radar, only about 1 percent are triple systems.

Source: JPL

Half Comet-Half Asteroid a Fluke? Nope

Images of known MBCs from UH 2.2-meter telescope data. Credit: Henry Hsieh

Back in 1996, astronomers discovered a strange object in the asteroid belt. They decided it was either a “lost” comet or an icy asteroid, as it ejected dust like a comet but had an orbit like an asteroid. No one had ever seen anything like the object, called 133P. Ever since it was found, astronomers have wondered if it was just an oddity — one of a kind. We now know it is not, and the discovery of more of these half asteroids/half comets means there is a new class of objects in our solar system.

One of these new objecst, 176P/LINEAR is also emitting dust as it orbits in the asteroid belt. It was found by Henry Hsieh at Queen’s University, Belfast in Northern Ireland. Hsieh has been working to figure out the unusual behavior of 133P. He hypothesized that either one of two things could explain the existence of the comet-asteroid: “(1.) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit, or (2.) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed,” Hsieh wrote in his paper. “If (1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if (2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity.”

Hsieh thought it was unlikely a comet could have been kicked around enough to end up in orbit in the asteroid belt, so he followed the assumption that 133P was a dynamically ordinary, yet icy main-belt asteroid. He set out to prove the hypothesis that 133P-like objects should be common and could be found by an well-designed observational survey.

Hsieh made 657 observations of 599 asteroids in the asteroid belt and found 176P/LINEAR. He also determined the asteroid is partially made of ice, which is being ejected following a collision with another object, thus the comet-like attributes.

Additionally, since there is evidence for past and even present water in main-belt asteroids, Hsieh says statistically there should be around 100 currently active Main Belt Comets (MBCs) as these objects are called, among the kilometer-scale, low-inclination, outer belt asteroid population.

The Technology Review blog offered suggestions for what to name these new objects that are half comet and half asteroid: “Comsteroids? Asteromets? Hsiehroids?”

Hseih’s paper,
Hseih’s website on MBCs
Sources: Technology Review Blog, arXiv

Keep Track of NEOs with New “Asteroid Watch” Website

With the recent impact on Jupiter, a lot of people out there have asteroids on their mind and wonder if one could possibly hit Earth. Now, NASA and JPL have a new website called “Asteroid Watch” which will keep everyone updated if any object approaches Earth. They’ve also created an Asteroid Watch Twitter account that Tweet updates on NEOs, plus there’s a downloadable widget as well.

“The goal of our Web site is to provide the public with the most up-to-date and accurate information on these intriguing objects,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at JPL.

“This innovative new Web application gives the public an unprecedented look at what’s going on in near-Earth space,” said Lindley Johnson, program executive for the Near-Earth Objects Observation program at NASA Headquarters in Washington.

Information is garnered from surveys and missions that detect and track asteroids and comets passing close to Earth. The Near-Earth Object Observation Program, commonly called “Spaceguard,” also plots the orbits of these objects to determine if any could be potentially hazardous to our planet.

There’s also another non-NASA Twitter feed called lowflyingrocks that lets you know about every Near Earth Object that passes within 0.2AU of Earth.

Source: JPL

How Big is Apophis?

Radar image of asteroid Apophis.

Question: How Big is Apophis?

Answer: In case you haven’t heard, Asteroid 99942 Apophis is a near Earth asteroid that astronomers think will make a close flyby to the Earth in 2029. When its trajectory was first calculated back in 2004, it had one of the closest visits to Earth astronomers had seen, and had a 2.7% chance of hitting the Earth.

But follow-up observations brought that risk down to 1 in 45,000. Right now, astronomers think that Apophis is essentially no risk to the Earth. In April, 2008 media reported that a 13-year old German student had caught a math mistake made by NASA, and the risk of an Earth strike was actually 1-45. This later turned out to be a hoax.

Because of its close approach to Earth, space advocacy societies, including the Planetary Society think that the Apophis asteroid would make an ideal target for a human mission, and allow engineers to test out strategies for moving asteroids away from dangerous Earth-crossing orbits.

So back to the original question, how big is Apophis? The best estimate puts it at 270 meters (885 feet across), and it has a mass of 2.1 x 1010 kg. To give you a sense of scale, the Eiffel Tower in Paris is 324 meters tall.

But now you know its mass and size, you’re probably wondering: what would happen to the Earth if it struck? NASA estimated that a strike by Apophis would release the equivalent of 880 megatons of energy. Just as a comparison, the object that carved out Meteor Crater in Arizona probably released 3-10 megatons of energy.

If Apophis struck land, it would flatten thousands of square km of land, killing millions of people if it hit a densely populated area. But it wouldn’t cause the kinds of long term climate destruction that 1 km and larger asteroids can do. If it hit an ocean, it would create devastating tsunamis in all directions.

Here’s an article explaining techniques that might be used to move an asteroid. And here’s NASA’s official page on Apophis.

1-in-75 Chance Of Tunguska-Size Impact On Mars


A 164-foot (50 meter) wide asteroid will be crossing the orbit of Mars at the end of January 2008. Currently, there is a 1-in-75 chance of the “Mars Crosser” hitting the Red Planet, and if it does, the 30,000 mile per hour speeding mass would generate a three megaton explosion (approximately the size of the terrestrial Tunguska impact over Siberia in 1908) and create a crater half-a-mile wide somewhere north of Meridiani Planum. So, the Mars Rover Opportunity will get a ringside seat should this once-in-a-thousand-year event occur…

NASA’s Near-Earth Object Office at the Jet Propulsion Laboratory (JPL) in Pasadena, California reported this month that a known Near Earth Asteroid (NEO) will be crossing the path of Mars on January 30, 2008. This puts asteroid “2007 WD5” in a special group of asteroids: “Mars Crossers“. NASA’s Near Earth Object Observation Program (or “Spaceguard” program) is intended to track asteroids that come close to the orbit of Earth, but also provides data for any asteroids tracked near our planetary neighbors.

Scientists are both excited and concerned by the possibility of an impact on Mars. Whilst this is a once in a lifetime opportunity to observe an impact of this size on Mars (remember the excitement at Shoemaker-Levy hitting Jupiter in 1994?), this event would eject millions of tons of dust into the Mars atmosphere, interfering with the Mars Expedition Rovers, and hindering orbital imaging of the planet. The Phoenix mission (currently en-route) will undoubtedly be affected. Looking far into the future, this event could have serious consequences for manned exploration.

“Right now asteroid 2007 WD5 is about half-way between the Earth and Mars and closing the distance at a speed of about 27,900 miles per hour […] Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid’s trajectory,” – Don Yeomans, manager of the NEO Office at JPL.

Although the odds are low, and the asteroid is expected to miss Mars by 30,000 km, asteroid hunters will be keeping a close eye on the progress of 2007 WD5 as it barrels closer and closer to the Red Planet and our robotic explorers.

Source: Near Earth Object Program