Keeping Bugs Away from Food
Springing forward
Flush-Free Fertilizer
Frogs and Toads
Crocodile Hearts
A Jellyfish's Blurry View
Listen and Learn
Lost Sight, Found Sound
Wired for Math
Carnivorous Birds
Chemistry and Materials
Big Machine Reveals Small Worlds
The solar system's biggest junkyard
Supergoo to the rescue
Fingerprint Evidence
The solar system's biggest junkyard
Hitting the redo button on evolution
Dinosaurs and Fossils
A Really Big (but Extinct) Rodent
Ancient Critter Caught Shedding Its Skin
Teeny Skull Reveals Ancient Ancestor
E Learning Jamaica
Results of GSAT are in schools this week
2014 GSAT Results for Jamaican Kids
E Learning in Jamaica WIN PRIZES and try our Fun Animated Games
Pollution at the ends of the Earth
Sky Dust Keeps Falling on Your Head
Flower family knows its roots
Swimming with Sharks and Stingrays
What is groundwater
Bald Eagles Forever
Finding the Past
Unearthing Ancient Astronomy
Meet your mysterious relative
Oldest Writing in the New World
Nurse Sharks
A Grim Future for Some Killer Whales
Food and Nutrition
How Super Are Superfruits?
Turning to Sweets, Fats to Calm the Brain
Chocolate Rules
GSAT English Rules
Order of Adjectives
Who vs. That vs. Which
Adjectives and Adverbs
GSAT Exam Preparation Jamaica
GSAT Scholarship
Preparing for the GSAT Exam
42,000 students will sit for the GSAT Exam in two weeks
GSAT Exams Jamaica Scholarships
2014 GSAT Results for Jamaican Kids
Access denied - Disabled boy aces GSAT
GSAT Exam Preparation
GSAT Mathematics
Math Naturals
10 Common Mistakes When Preparing for the GSAT Math Test
Setting a Prime Number Record
Human Body
A Long Trek to Asia
What the appendix is good for
Cell Phone Tattlers
Giant Squid
Giant Panda
St. Bernards
Doberman Pinschers
How children learn
The Surprising Meaning and Benefits of Nursery Rhymes
Raise a Lifelong Reader by Reading Aloud
The Particle Zoo
Thinner Air, Less Splatter
Extra Strings for New Sounds
The algae invasion
Fast-flying fungal spores
A Change in Leaf Color
Space and Astronomy
Asteroid Lost and Found
Planet Hunters Nab Three More
A Puffy Planetary Puzzle
Technology and Engineering
Toy Challenge
Beyond Bar Codes
Young Scientists Take Flight
The Parts of Speech
Adjectives and Adverbs
What is a Preposition?
What is a Noun
How to Fly Like a Bat
Seen on the Science Fair Scene
Flying the Hyper Skies
Science loses out when ice caps melt
Antarctica warms, which threatens penguins
Catching Some Rays
Add your Article

The two faces of Mars

When you look up at the night sky, it's hard to imagine the violent, chaotic place the solar system was billions of years ago. It looks quiet and peaceful now, but when the solar system first took shape, asteroids and other objects regularly slammed into each other, sometimes knocking off huge chunks of rock. Some of these eventually became moons, and left the surfaces of the planets forever changed. Now, scientists say one of these massive collisions knocked off much of the top layer of the northern hemisphere of Mars, our planetary neighbor. Their findings answer a question that has long puzzled scientists: Why do the Red Planet's northern and southern hemispheres look so different from one another? The debate started more than 30 years ago, when NASA scientists launched the Viking spacecraft into orbit around Mars. The spacecraft sent back the first close-up maps and images anyone had ever seen of the Martian surface. Surprisingly, those images showed that northern Mars looks very different from southern section of the planet. While the north was flat and smooth, the south was rugged, dotted with craters and mountains. Another NASA spacecraft, the Mars Global Surveyor, later showed that the planet's crust is also thicker in the south than in the north. In fact, the entire southern hemisphere of Mars is about four kilometers higher than the northern hemisphere. What could account for these observations? It's been a topic of debate for decades. Some suggested that processes deep below the planet's surface gave Mars different kinds of crust in the two hemispheres. Others thought the impact from many colliding meteorites, comets or other objects could have shaved off four kilometers of crust from the northern hemisphere over time. Still another pair of scientists suggested a single impact from just one object could have created the planet's two faces. By studying data from two spacecraft, NASA's Mars Odyssey and the Mars Global Surveyor, a team of planetary scientists was able to look below the surface of a recent lava flow on the Martian surface. Just like on Earth, volcanoes periodically spew lava over the planet's surface, and on Mars, this lava previously blocked scientists' view of the planet's underlying bedrock. Below the lava, they found a huge crater the size of Asia, Australia and Europe combined running the length of the boundary between the flat northern hemisphere and the bumpy southern hemisphere. It's an important clue, scientists say. "Finding this elliptical boundary is a smoking gun," says Jeffrey Andrews-Hanna, a planetary scientist at the Massachusetts Institute of Technology. "There is only one known way to get a shape like this: impact." The impact theory gets even more support from additional findings from other scientists. Two other groups of researchers used computer programs to predict what kind of impact could have given Mars its dual appearance. They ran a series of computerized scenarios in which they slammed different objects into the planet at different speeds and angles. They estimated that a Pluto-sized object traveling at 32,000 kilometers per hour would have generated enough energy to blast off the crust of the planet's northern half. "Something big smacked into Mars and stripped half the crust off the planet," says Francis Nimmo, a planetary scientist at the University of California, Santa Cruz who ran some of the computer simulations. These new observations still do not disprove the idea that processes deep below the planet's surface could have caused the difference in the planet's two halves. But, says Steven Squyres, a planetary scientist at Cornell University, "it's nice to see an old idea dusted off and turned into something with real physical plausibility."

The two faces of Mars
The two faces of Mars

Designed and Powered by™