|Operator||Japan Aerospace Exploration Agency (JAXA)|
|Mission type||orbiter and up to 4 small landers|
|Launch date||Proposed for 2016 - 2020|
|Orbital period||12.33 hours (1/2 sol)|
MELOS (Mars Exploration with a Lander-Orbiter Synergy) is a proposed Japanese planetary exploration mission that would investigate the evolution of Martian atmosphere, the water and climate of Mars.
The mission's objective is to increase understanding on the composition of the interior and surface of Mars, as well as its atmosphere and surrounding space.
The MELOS mission would consist of an orbiter and up to 4 small landers; all elements would be launched together on the same rocket. The orbiter would study the atmosphere, its and interactions with the solar wind, and image the current weather. Each of the four stationary landers would be deployed on pre-determined landing sites and perform different measurements: 
- Orbiter — Meteorology
- Lander A — Surface
- Lander B — Astrobiology
This lander would analyse soil near a methane vent. The proposed method is to use fluorochrome dye and a microscope to stain and scan for proteins and cellular membranes. The target sensitivity would be 10 cells / 1 g of soil (compared to 104 cells / 1 g in Earth desert). It would also detect other organic biosignatures.
- Lander C — Interior
- Lander D — Sample return
Sample return in late 2020s.
This proposed mission by the Japan Aerospace Exploration Agency (JAXA), aims to understand the geological evolution of Mars and to answer the fundamental question "Why (and how) is Mars different from the Earth?". MELOS would attempt to determine if Mars had a warm and wet environment in its early stages.
- "Japan’s Mars Exploration Plan: MELOS" (PDF), The 2009 MEPAG Meeting, March 2009, retrieved 2012-10-17
- "MELOS: Japan’s Mars Exploration Plan ~ Updates on MELOS1 ~" (PDF), MEPAG 2012, Washington D.C.: Japan Aerospace Exploration Agency (JAXA), February 2012, retrieved 2012-10-18
- MELOS: Japan’s Mars Exploration Plan for 2020’s. MEPAG in Lisbon, Portugal (16-17 June 2011)
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