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How did life begin and evolve on Earth, and has it evolved elsewhere in the Solar System?

Microbial life forms have been discovered on Earth that can survive and even thrive at extremes of high and low temperature and pressure, and in conditions of acidity, salinity, alkalinity, and concentrations of heavy metals that would have been regarded as lethal just a few years ago. These discoveries include the wide diversity of life near sea–floor hydrother­mal vent systems, where some organisms live essentially on chemical energy in the absence of sunlight. Similar environments may be present elsewhere in the Solar System.

Under­standing the processes that lead to life, however, is complicated by the actions of biology itself. Earth’s atmosphere today bears little resemblance to the atmosphere of the early Earth, in which life developed; it has been nearly reconstituted by the bacteria, vegetation, and other life forms that have acted upon it over the eons. Fortunately, the Solar System has preserved for us an array of natural laboratories in which we can study life’s raw ingredients — volatiles and organics — as well as their delivery mechanisms and the prebiotic chemical processes that lead to life. We can also find on Earth direct evidence of the interactions of life with its environments, and the dramatic changes that life has undergone as the planet evolved. This can tell us much about the adaptability of life and the prospects that it might survive upheavals on other planets.

Related missions:

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DivisionNameLaunch DatePhase
Planets Cassini
The Cassini Mission is in the midst of a detailed study of Saturn, its rings, its magnetosphere, its icy satellites, and its moon Titan. Cassini also delivered a probe (called Huygens, provided by the European Space Agency) to Titan, and ...
19971015 October 15, 1997 3Operating
Planets Deep Impact
The Deep Impact mission was selected as a Discovery mission in 1999. The spacecraft was launched aboard a Delta II rocket on January 12, 2005 and left Earth’s orbit toward Comet Tempel 1. The spacecraft consists of two main sections, ...
20050112 January 12, 2005 4Past
Planets Epoxi
Extrasolar Planet Observation and Deep Impact Extended Investigation EPOXI is a follow-on mission to Deep Impact. This mission is part of SMD's Discovery program.
20050112 January 12, 2005 3Operating
Planets ExoMars Trace Gas Orbiter
The European Space Agency plans for the ExoMars rover to grind samples of Martian soil to fine powder and deliver them to a suite of analytical instruments, including Urey that will search for signs of life.
Planets Lunar Reconnaisance Orbiter
The Lunar Reconnaissance Orbiter (LRO) is the first mission in NASA's plan to return to the moon and then to travel to Mars and beyond. This mission is part of SMD's Robotic Lunar Exploration program.
20090617 June 17, 2009 3Operating
Planets Mars Express (ASPERA-3)
Mars Express is exploring the atmosphere and surface of Mars from polar orbit. The mission's main objective is to search for sub-surface water from orbit and deploy a lander onto the Martian surface.
20030602 June 02, 2003 3Operating
Planets Mars Global Surveyor
Mars Global Surveyor is returning an unprecedented amount of data regarding Mars' surface features, atmosphere, and magnetic properties. Scientists are using the data gathered from this mission both to learn about the Earth by comparing it to Mars, and to ...
19961107 November 07, 1996 4Past
Planets Mars Science Laboratory
NASA proposes to develop and to launch a roving long-range, long-duration science laboratory that will be a major leap in surface measurements and pave the way for a future sample return mission. The mission will also demonstrate the technology for ...
20111126 November 26, 2011 3Operating
Planets MAVEN
The Mars Atmosphere and Volatile Evolution Mission (MAVEN), set to launch in 2013, will explore the planet’s upper atmosphere, ionosphere and interactions with the sun and solar wind. Scientists will use MAVEN data to determine the role that loss of ...
20131118 November 18, 2013 2Development
Planets Phoenix
Phoenix seeks to verify the presence of the Martian Holy Grail: water and habitable conditions.
20070804 August 04, 2007 4Past