Featured Research

from universities, journals, and other organizations

Evidence Of Massive Asteroid Impact On Mars Supported By Computer Simulations

Date:
June 26, 2008
Source:
University of California - Santa Cruz
Summary:
The dramatic differences between the northern and southern hemispheres of Mars have puzzled scientists for 30 years. One of the proposed explanations -- a massive asteroid impact -- now has strong support from computer simulations carried out by two groups of researchers.

The northern hemisphere of Mars is low (blue) and smooth, while the southern hemisphere is high (red) and heavily cratered.
Credit: Image courtesy of NASA

The dramatic differences between the northern and southern hemispheres of Mars have puzzled scientists for 30 years. One of the proposed explanations--a massive asteroid impact--now has strong support from computer simulations carried out by two groups of researchers. Planetary scientists at the University of California, Santa Cruz, were involved in both studies, which appear in the June 26 issue of Nature.

"It's a very old idea, but nobody had done the numerical calculations to see what would happen when a big asteroid hits Mars," said Francis Nimmo, associate professor of Earth and planetary sciences at UCSC and first author of one of the papers.

Nimmo's group found that such an impact could indeed produce the observed differences between the Martian hemispheres. The other study used a different approach and reached the same conclusion. Nimmo's paper also suggests testable predictions about the consequences of the impact.

The so-called hemispheric dichotomy was first observed by NASA's Viking missions to Mars in the 1970s. The Viking spacecraft revealed that the two halves of the planet look very different, with relatively young, low-lying plains in the north and relatively old, cratered highlands in the south. Some 20 years later, the Mars Global Surveyor mission showed that the crust of the planet is much thicker in the south and also revealed magnetic anomalies present in the southern hemisphere and not in the north.

"Two main explanations have been proposed for the hemispheric dichotomy--either some kind of internal process that changed one half of the planet, or a big impact hitting one side of it," Nimmo said. "The impact would have to be big enough to blast the crust off half of the planet, but not so big that it melts everything. We showed that you really can form the dichotomy that way."

Nimmo's group includes UCSC graduate student Shawn Hart, associate researcher Don Korycansky, and Craig Agnor of Queen Mary University, London. The other paper is by Margarita Marinova and Oded Aharonson of the California Institute of Technology and Erik Asphaug, professor of Earth and planetary sciences at UCSC.

The quantitative model used by Nimmo's group calculated the effects of an impact in two dimensions. Asphaug's group used a different model to calculate impacts in three dimensions, but with lower resolution (i.e., less detail in the simulation).

"The two approaches are very complementary; putting them together gives you a complete picture," Nimmo said. "The two-dimensional model provides high resolution, but you can only look at vertical impacts. The three-dimensional model allows nonvertical impacts, but the resolution is lower so you can't track what happens to the crust."

Most planetary impacts are not head-on, Asphaug said. His group found a "sweet spot" of impact conditions that result in a hemispheric dichotomy matching the observations. Those conditions include an impactor about one-half to two-thirds the size of the Moon, striking at an angle of 30 to 60 degrees.

"This is how planets finish their business of formation," Asphaug said. "They collide with other bodies of comparable size in gargantuan collisions. The last of those big collisions defines the planet."

According to Nimmo's analysis, shock waves from the impact would travel through the planet and disrupt the crust on the other side, causing changes in the magnetic field recorded there. The predicted changes are consistent with observations of magnetic anomalies in the southern hemisphere, he said.

In addition, new crust that formed in the northern lowlands would be derived from deep mantle rock melted by the impact and should have significantly different characteristics from the southern hemisphere crust. Certain Martian meteorites may have originated from the northern crust, Nimmo said. The study also suggests that the impact occurred around the same time as the impact on Earth that created the Moon.

This research was funded by NASA.


Story Source:

The above story is based on materials provided by University of California - Santa Cruz. Note: Materials may be edited for content and length.


Cite This Page:

University of California - Santa Cruz. "Evidence Of Massive Asteroid Impact On Mars Supported By Computer Simulations." ScienceDaily. ScienceDaily, 26 June 2008. <www.sciencedaily.com/releases/2008/06/080625140659.htm>.
University of California - Santa Cruz. (2008, June 26). Evidence Of Massive Asteroid Impact On Mars Supported By Computer Simulations. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2008/06/080625140659.htm
University of California - Santa Cruz. "Evidence Of Massive Asteroid Impact On Mars Supported By Computer Simulations." ScienceDaily. www.sciencedaily.com/releases/2008/06/080625140659.htm (accessed September 19, 2014).

Share This



More Space & Time News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

MIT BioSuit A New Take On Traditional Spacesuits

MIT BioSuit A New Take On Traditional Spacesuits

Newsy (Sep. 19, 2014) The MIT BioSuit could be an alternative to big, bulky traditional spacesuits, but the concept needs some work. Video provided by Newsy
Powered by NewsLook.com
Boeing, SpaceX to Send Astronauts to Space Station

Boeing, SpaceX to Send Astronauts to Space Station

AFP (Sep. 17, 2014) NASA selected Boeing and SpaceX on Tuesday to build America's next spacecraft to carry astronauts to the International Space Station (ISS) by 2017, opening the way to a new chapter in human spaceflight. Duration: 01:13 Video provided by AFP
Powered by NewsLook.com
East Coast Treated To Rare Meteor Sighting

East Coast Treated To Rare Meteor Sighting

Newsy (Sep. 16, 2014) Numerous residents along the East Coast reported seeing a bright meteor flash through the sky Sunday night. Video provided by Newsy
Powered by NewsLook.com
Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins