VOA慢速英语:Many Life Forms Discovered Deep under Antarctic Ice

constraint – n. something that limits or restricts someone or something

subglacial - adj. under a glacier (a large area of thick ice and snow)

tractor – n. heavy machinery often used on a farm

converge – v. to come together; move toward one point and join together

around the clock – adj. happening or continuing all day and all night

organism –n. an individual living thing