A tiny region has been spotted in the United States generating an anomalously high concentration of methane, a potent greenhouse gas.
Using data from the European Space Agency's Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument on board ENVISAT, scientists from NASA and the University of Michigan discovered the hotspot near the Four Corners intersection of Arizona, Colorado, New Mexico and Utah, covering approximately 2,500 square miles (6,500 square kilometers).
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ENVISAT was operational from in 2002, but ground controllers lost contact in 2012, ending the decade-long mission. The defunct satellite remains in orbit today.
During its operational lifetime, SCIAMACHY collected methane data, and the researchers studied data gathered between 2003-2009 to show that the Four Corners region had emitted around 590,000 metric tons of methane into the atmosphere. That's 3.5 times more methane than what was predicted to be generated by the area.
To verify the remote satellite data, the researchers compared their results with a Total Carbon Column Observing Network ground station, operated by the Department of Energy's Los Alamos National Laboratory in New Mexico, which verified the findings.
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The researchers note that the huge methane release data predates extensive hydraulic fracturing, known as fracking, that is currently being carried out in the area.
So if it's not fracking, what's causing this leakage of methane into the atmosphere?
In a paper published in the journal Geophysical Research Letters, the researchers attribute the hotspot to leaks in the natural gas production and processing industry that can be found extensively in the New Mexico's San Juan Basin. The basin, as it turns out, "is the most active coal-bed methane production area in the country," according to a NASA Jet Propulsion Laboratory (JPL) news release.
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Coal-bed methane is found in the cracks and pores inside coal deposits and can present a deadly, explosive hazard as it seeps out of the rocks. Since the 1970s, techniques have been developed to extract these methane deposits and use the supply as fuel. As of 2012, coal-bed methane accounted for 8 percent of the US natural gas supply.
"The results are indicative that emissions from established fossil fuel harvesting techniques are greater than inventoried," said Eric Kort of the University of Michigan, Ann Arbor, and lead author of the published study. "There's been so much attention on high-volume hydraulic fracturing, but we need to consider the industry as a whole."
Methane leaks are hard to detect as the gas is colorless and odorless, so special instruments are required to detect its release from natural gas extraction sites. Natural gas is up to 98 percent methane.
This is where Earth-observing satellites come in.
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"Satellite data cannot be as accurate as ground-based estimates, but from space, there are no hiding places," said Christian Frankenberg of JPL, who first noticed the methane hotspot years ago in the SCIAMACHY data. Once corroborating data was acquired, it became clear that the Four Corners signal was very real.
With climate change impacting every corner of the globe, it's becoming increasingly important for space-based assets to seek-out and pinpoint sources of greenhouse gas emissions if we are ever to find a solution to this increasingly acute global problem.