He found, against all expectations, that certain hardy microbes could thrive in geothermal springs hot enough to poach an egg. They specifically searched for genes that may help microbes survive hostile conditions, such as extreme temperatures or the absence of oxygen. These are the molecular building blocks of life on Earth and may be rare in some otherwise-habitable extraterrestrial environments. According to McKay, extraterrestrial environments for life may be like those found on Earth, or they could differ vastly. “If [extraterrestrial life] is too [similar] to our life on Earth, people will argue that it is something that we brought with us.