NASA on Friday showed off its Mars 2020 rover, whose official name will be chosen early next year. NASA will in February ship the rover to Florida’s Kennedy Space Center, where its three sections will be fully assembled. A July launch will send the rover to a dry lake bed on Mars that is bigger than the island of Manhattan. […] The four-wheeled, car-sized rover will scour the base of Mars’ Jezero Crater, an 820-foot-deep (250-meter-deep) crater thought to have been a lake the size of Lake Tahoe, once the craft lands in February 2021. The crater is believed to have an abundance of pristine sediments some 3.5 billion years old that scientists hope will hold fossils of Martian life.
Given that the oldest fossils (that are generally recognised) on Earth are about 3.5-billion years old1, this is an optimistic goal.
Stromatolites found in Canada.