Exxon Mobil announced that it would acquire XTO Energy in an all-stock deal worth $41 billion. The acquisition is viewed as Exxon’s decision to enter the domestic onshore gas shale play, which to date has been developed almost exclusively by independent producers. But the deal includes an exit clause in the event Congress passes legislation that would make hydraulic fracturing illegal or “commercially impracticable.” Shale gas development would be impossible without hydraulic fracturing technology. Bills are pending in Congress (known as the FRAC Act) to subject fracturing to federal regulation under the Safe Drinking Water Act. The bills would require companies to publicly disclose the chemicals used in frac fluids. And U.S. Rep. Ed Markey, Dem. Massachusetts, said he would hold hearings in the House Energy and Commerce Committee to review the Exxon-XTO deal and to address environmental concerns about hydraulic fracturing.