Impact Events » The Wembo-Nyama Feature
The Wembo-Nyama Feature - Democratic Republic of Congo
This circular feature could be one of the largest asteroid impact sites on Earth
Republished from an March, 2010 press release by NASA Earth Observatory
What Earth Processes Produce Circular Features?
In the center of the Democratic Republic of Congo, the Unia River flows around a circular structure
known as the Wembo-Nyama feature. Several things in nature leave a circular footprint such as this,
including volcanoes and uplifted domes. However, Italian scientists from the University of Padova believe
that the Wembo-Nyama feature is an impact crater. If the 36-46-kilometer-wide feature is a crater, it is
among the largest in the world.
Popular! World Map of Asteroid Impact Craters
Satellite Image of the Structure
The river's path highlights the circular structure in this natural-color image acquired by the Landsat-7
satellite on April 1, 2000. Fingers of deep green forest extend from the river, probably along tributaries
that drain the elevated structure. In places, the forest has been replaced with spots of bright green farm
land. The land that isn't forested or farmed is tan, an indication that little is growing.
The Drainage Pattern Reveals the Crater
The drainage pattern exhibited in this image is typical of craters in tropical regions, the University of Padova
scientists told BBC News. The river flows through a depression, while the center of the circle is elevated.
a meteor strikes Earth, it creates an explosion that compresses the rock in a circular region. In deep, large
craters, the rock in the center rebounds, creating a dome of uplifted rock.
Confirming the Impact Origin
Scientists have to sample the rock in the Wembo-Nyama feature to confirm whether or not it is an impact crater
and when it formed. Its size suggests that, if the structure is an impact crater, it was created by a meteor
measuring about two kilometers across.
|The study found in one test that after the first large rainstorm in October, only 4 percent of the precipitation entering the soil ended up in the stream – 96 percent was taken up and held tightly by soil around plants to recharge soil moisture. A month later when soil moisture was fully recharged, 55 percent of precipitation went directly into streams. This is contrary to widely-held assumptions of how water behaves in soils. USGS image.