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Atmosphere, Biosphere, Lithosphere, Space/Planetary Science



In 1980 Nobel laureate Luis Alvarez, his geologist son Walter, and paleontologist Helen Michael published their discovery of a world wide Iridium layer at the K-T boundary. Iridium is rarely found on Earth but is common to space objects. They hypothesized that the Iridium had arrived on Earth in the form of a giant meteor or comet. This giant impact, they said, could have put enough dust in the atmosphere to cool the Earth and may have led to the mass extinction around the K-T boundary. The problem was that no-one knew of such an impact.

About ten years later, petroleum geologists discovered in the Yucatan Peninsula what they thought to be a giant impact crater at the K-T boundary. The impact crater is about 110 miles (180 km) across and is one of the largest known craters in the solar system. An asteroid large enough to create this crater was probably 10 km (six miles) across. The Chicxulub (pronounced CHIK-shu-loob) crater served as the "smoking gun" in support of the Alverez" suggestion that a giant meteor impacted the Earth at the K-T boundary.

Although the debate still rages, many scientists suggest that the asteroid impact at the end of the Cretaceous Period caused the demise of dinosaurs . The scenario played out along these lines: the asteroid or comet, struck the shallow sea in a blinding fireball! A vast cone of red-hot rock and steam blasted upward above the atmosphere only to fall back and flare again upon re-entry. Vast forest fires ignited all over the world by the intense heat! Mile-high waves from the impact site roared across the shorelines of North and South America, sweeping everything away! Huge clouds of dust quickly spread from the impact site to cover the whole Earth!

The asteroid impact and resulting heat wave would have caused giant forest fires worldwide. Thick clouds from the dust thrown up by the impact and clouds of smoke from fires started by the heat of the impact explosion covered the whole Earth for at least six months to a year. A lack of sunlight killed ocean algae and plants on the land not burned by the fires. Further extinctions were caused by chemicals from the asteroid and heated air formed acid rain that poisoned rivers, lakes and oceans.

Finally the surface of Earth was hidden by clouds of dust and steam. As the global fires died out below the clouds, the whole surface of Earth grew dark and cold. While the impact and its results took less than a day, but it would be six months before sunlight reached the ground again! This animation from hypothesizes about what might have happened.

Your team has been tasked with developing an Earth system analysis of the Chicxulub Impact, and then determining the risk of a similar catastrophic event in the future.



The Chicxulub impact has generated many hypotheses about the sequence of events and exactly how life changed so abruptly (see for example: Brother's paper Concerning Mass Extinction Across the K-T Boundary.)

Whether or not the mass extinctions occurred due to a single impact, multiple impacts or other Earth events, scientists tell us there is a 100% probability of another Earth impact from asteroids or comets. NASA's stated goal (Pilcher 1998) is to find 90% of the larger NEAs (>1 km diameter) by 2008. How many remain to be accounted for? According to JPL, as of January 13, 2008, 5136 Near-Earth objects have been discovered. 732 of these NEOs are asteroids with a diameter of approximately 1 kilometer or larger. Also, 908 of these NEOs have been classified as Potentially Hazardous Asteroids (PHAs). Based on your Earth system analysis of the Chicxulub impact, project the scenario of a present day impact of a NEO greater than one kilometer in diameter.


Date: 1/16/2008

Scenario Images:

Chicxulub Crater
Radar topography reveals the 180 kilometer (112 mi) ring of the crater; clustered around the crater's trough are numerous sinkholes, suggesting a prehistoric oceanic basin in the depression left by the impact. Image: courtesy NASA/JPL-Caltech



Asteroid and Comet Impact Hazards (Cycle A)
NASA Ames Research Center site on Near Earth Objects and impact hazards. Contains news, bibliography, governments studies and related links. The latter is rich in sites dealing with Near Earth Objects and Near Earth Asteroids.


Asteroids: Origin and Evolution (Cycle A)
Asteroids are fundamental to our understanding of planet formation and ultimately why life exists on Earth. They are the most direct remnants of the original building blocks that formed the planets of our Solar System and are relatively pristine samples of the initial conditions in the solar nebula 4.6 billion years ago. On the OSIRIS-REx site you will find much information about asteroids, and the questions scientists are asking.

The OSIRIS-REx spacecraft will travel to a near-Earth carbonaceous asteroid (101955) 1999 RQ36, study it in detail, and bring back a sample (at least 60 grams or 2.1 ounces) to Earth.


Coordinate systems and mapping the solar system (Cycle A)
Understanding the orbits of asteroids requires an understanding of the 3-dimensional nature of the solar system. The interactive information provided will help you understand the coordinate system used to describe objects in the solar system by relating them to earth's coordinate system.


Earth Impact Effects Program (Cycle A)
This interactive program from the University of Arizona Space Imagery allows you to explore the environmental and biological consequences associated with various impact events. This is a new area of study, so information of this type is not yet available for many impact craters. However, as new results appear in the peer-reviewed literature, details for each crater will be added to this site as examples.


Large Synoptic Survey Telescope Near-Earth Objects (Cycle A)
It is widely recognized that the earth hosts a number of impact sites, and there are tens of thousands of uncharted Potentially Hazardous Asteroids (PHAs) of significant size (above 140m) orbiting within our solar system. The Large Synoptic Survey Telescope, scheduled to see first light in 2014, will extend the boundaries of our solar system and map over 90% of the potentially hazardous asteroids in the solar system, reducing the hazard posed by currently undetected objects. The LSST site discusses Near Earth Object (NEO) detection.


NASA's Near Earth Object Program (Cycle A)
Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighborhood. Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system between the orbits of Mars and Jupiter.

To plot the orbit of NEOs, go to JPL Small-body Database Browser. Search for an asteroid or comet and then click on "Orbit Diagram."


The Chicxulub Crater (Cycle A)
Covers the sequence of finding the crater. Contains many good resources.


Dealing with the Impact Hazard (Cycle B)
Comprehensive technical summary by David Morrison at the NASA Astrobiology Institute and colleagues of the asteroid impact hazard as of mid-2002.


Earth Impact Database (Cycle B)
The Earth Impact Database comprises a list of confirmed impact structures from around the world. The database was conceived in its earliest form when a systematic search for impact craters was initiated in 1955 by the Dominion Observatory, Ottawa, under the direction of Dr. Carlyle S. Beals


Planetary Society: Making You A Part of the Next Age of Exploration (Cycle B)
The Planetary Society, founded in 1980 by Carl Sagan, Bruce Murray, and Louis Friedman, inspires and involves the world's public in space exploration through advocacy, projects, and education. Today, The Planetary Society is the largest and most influential public space organization group on Earth. Dedicated to exploring the solar system and seeking life beyond Earth, The Planetary Society is non-governmental and nonprofit and is funded by the support of its members.


White Paper on The Comet/Asteroid impact hazard: A Systems Approach (Cycle B)
Discusses impacts, the detection and impact effects of NEO's, mitigation and recommendations. By Chapman and Durda, Office of Space Studies, Southwest Research Institute and Gold, Johns Hopkins University Applie Physics Laboratory.


Asteroids: Exploring the Wilderness of Rocks (Cycle C)
This website provides information and resources about an exciting new education project under development at the National Optical Astronomy Observatory . In this project, students will explore the thousands of small bodies that roam space between the planet and the asteroids to understand the Earth, its rocks and history, and its place in the Solar System.


Astronomical images for finding asteroids (Cycle C)
Learn about asteroids, the wandering space rocks in our own Solar System, then look through SkyServer to find them. SkyServer from the Sloan Digital Sky Survey (SDSS) has more than 100,000 asteroids for you to find. By analyzing images taken using colored astronomical filters you can locate asteroids in the Sloan Digital Sky Survey data.


Earth-crossing asteroids (Cycle C)
On March 23, 1989 the 300 meter (1,000-foot) diameter Apollo asteroid 4581 Asclepius (1989 FC) missed the Earth by 700,000 kilometers (400,000 miles) passing through the exact position where the Earth was only 6 hours before. If the asteroid had impacted it would have created the largest explosion in recorded history, thousands of times more powerful than the Tsar Bomba, the largest hydrogen bomb ever detonated.

An Earth-Crossing Asteroid (ECA), is an asteroid that is capable of coming very near to the Earth at any point in the future. Orbits of asteroids can be determined by using astronomical databases such as the Sloan Digital Sky Survey. The essential aspect is whether or not the perihelia of asteroids are less than the Earth's perihelion and that the aphelia are greater than the Earth's aphelion. The Sloan Digital Sky Survey (SDSS) provides raw data from their telescope that can be searched using a query language (SQL).

Query to find Earth-crossing asteroids in the SDSS DR3_MOC by Jordan Raddick & Andy Puckett, Jan 31, 2008

Go to
Then copy and paste this SQL Code to generate a table of Earth-crossing asteroids from Data Release 3.

moID as id,
a_osc as semimajor_axis,
e_osc as ellipticity,
i_osc as inclination
from DR3_MOC
(a_osc * (1-e_osc) < 0.983289891)
AND (a_osc * (1+e_osc) > 1.0167103335)


Sample Investigations:


Asteroid WISE (Cycle A)
Investigations for high school...a collaboration of the NASA WISE mission with the Lawrence Hall of Science
Hands-On Universe project.
Difficulty: intermediate


Chicxulub Impact Data Mapping (Cycle A)
Students use data sets to infer the presence of the Chicxulub impact crater. Students plot a contour map with gravity data points, map reflection seismic profiles and compare relative abundances of marine life above above and below the KT boundary.

Difficulty: intermediate


Explorers Guide to Impact Craters (Cycle A)
Join us in the scientific exploration of impact cratering, one of the most common and important geological processes in the Solar System.
Difficulty: beginner


Impact Craters: Teacher Page (Cycle B)
This activity teaches students how to determine the factors affecting the appearance of impact craters and ejecta. The Teacher Page contains background information on crater formation, definitions of crater terminology, activity preparation and in class instructions (materials and experiment procedures are on the Student Page of this activity), links to the Data Chart and Graph required for the experiment.
Difficulty: beginner


Mystery of the Chicxulub Crater: Animation Shows Liquid Impact (Cycle B)
This news article from reviews older articles on evidence for the impact hypothesis of dinosaur extinction at the end of the Cretaceous. The article contains hyperlinks to older, reviewed articles, digital images of the hypothesized impact and a link where the reader can post their opinion on the hypothesis.
Difficulty: intermediate


Impact Craters: Students Page (Cycle C)
This activity teaches students how to determine the factors affecting the appearance of impact craters and ejecta.

Difficulty: intermediate


Interactive Earth Impact Effects Program (Cycle C)
An easy-to-use, interactive web site for estimating the regional environmental consequences of an impact on Earth. This program will estimate the ejecta distribution, ground shaking, atmospheric blast wave, and thermal effects of an impact as well as the size of the crater produced.
Difficulty: intermediate


TEACH Engineering Resources for K-12: Asteroid Impact, Grades 6-8 (Cycle C)
Asteroid Impact is an 8-10 class long (350-450 min) earth science curricular unit where student teams are posed with the scenario that an asteroid will impact earth. They must design the location and size of underground caverns to save the people from uninhabitable earth for one year. Driven by this adventure scenario, student teams (1) explore general and geological maps, (2) determine the area of their classroom to help determine the cavern size required, (3) learn about map scales, (4) test rocks, (5) identify important and not-so-important rock properties for underground caverns, and (6) choose a final location and size. The unit also reinforces a number of math, reading and writing standards.
Difficulty: beginner




  • Science
    National Science Education Standards - Science Content Standards The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
      The understandings and abilities associated with the following concepts and processes need to be developed throughout a student's educational experiences:
      • Evidence, models, and explanation
      • Constancy, change, and measurement
      • Form and function
      • Science as Inquiry (Std A)
        • Abilities necessary to do scientific inquiry
        • Understanding about scientific inquiry
      • Earth and Space Science (Std D)
        • Structure of the earth system
        • Earth in the solar system
      • Science and Technology (Std E)
        • Abilities of technological design
        • Understanding about science and technology
      • Science in Personal and Social Perspectives (Std F)
        • Natural hazards
        • Risks and benefits
      • History and Nature of Science (Std G)
        • Science as a human endeavor
        • Nature of science
        • History of science
      • Science as Inquiry (Std A)
        • Understanding about scientific inquiry
      • Physical Science (Std B)
        • Structure and properties of matter
        • Motions and forces
        • Conservation of energy and increase in disorder
        • Interactions of energy and matter
      • Earth and Space Science (Std D)
        • Origin and evolution of the earth system
        • Origin and evolution of the universe
      • Science and Technology (Std E)
        • Understanding about science and technology
      • Science in Personal and Social Perspectives (Std F)
        • Natural and human-induced hazards
      • History and Nature of Science (Std G)
        • Science as a human endeavor
        • Nature of scientific knowledge
        • Historical perspectives
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