The National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) is releasing an Announcement of Opportunity (AO) entitled Mars 2020 Investigations to solicit proposals for investigations for a space flight mission to Mars, to be launched in July/August 2020. The full text of the AO and any appendices are available electronically at the NASA Solicitation and Proposal Integrated Review and Evaluation System (NSPIRES) website (http://nspires.nasaprs.com/ ). Links to the AO and additional information about the intent and the capabilities of the Mars 2020 rover are located at the Mars 2020 Acquisition Website (http://soma.larc.nasa.gov/mars2020 ). Investigations comprised of individual instruments or multiple instruments (suites) may respond to the overall Mars 2020 objectives to explore and quantitatively assess Mars as a potential habitat for life, to search for signs of past life, to collect carefully selected samples for possible future return to Earth, and to prepare for future human exploration of Mars. The Mars 2020 Investigations AO solicits flight investigations for which each Principal Investigator is responsible for a complete space flight investigation, including instrument hardware, mission operations, and data analysis. Although individual PI-managed instrument science investigations do not have a predetermined cost cap, the total allocated cost for all the SMD-funded investigations selected is approximately $100M in Real Year (RY) dollars for Phases A through D. Additional funding of approximately $60M RY is allocated for investigation in Phase E. Additionally, exploration technology investigations, jointly funded by the Human Exploration and Operations Mission Directorate (HEOMD) and Space Technology Mission Directorate (STMD) may be selected at a total cost of approximately $30M in RY dollars, including Phase E costs. The total payload resources, including mass, power, and data for the instrument complement, will be provided in a Payload Information Package (PIP) posted to the Mars 2020 Acquisition Website. Note that the Mars 2020 Investigations AO may contain provisions that differ from this notice, in which case those in the AO will take precedence. Participation in this AO is open to all categories of organizations (U.S. and non-U.S.), including educational, industrial, and not-for-profit organizations, Federally Funded Research and Development Centers, University Affiliated Research Centers, NASA centers, the Jet Propulsion Laboratory, and other Government agencies. Principal Investigators are responsible for, and may assemble their investigation teams from, any of these organizations. A preproposal conference is scheduled for October 8, 2013, via video/teleconference from Washington, DC. Notices of Intent (NOIs) are required and are due October 15, 2013. Proposals are due December 23, 2013. Contracting Office Address: NASA Goddard Space Flight Center, NASA Headquarters Acquisition Branch, Code 210.H, Greenbelt, MD 20771