The GBU-57 Massive Ordnance Penetrator (MOP) is a 30,000-pound (13,600 kg)

guided bomb designed to penetrate deep into the earth and 

destroy underground targets, such as nuclear facilities.  

The MOP is the largest conventional bomb in the US arsenal. 

The MOP was developed in the 2000s as concerns grew over Iran's nuclear program. 

The bomb is designed to penetrate up to 200 feet (61 m) of earth and concrete. 

The MOP is carried by the B-2 Spirit stealth bomber. 

The MOP has never been used in combat. 

However, it has been deployed to the Middle East in response to the tensions between the US and Iran.