We have two Mars orbiters arriving at Mars later this month (21 and 23 September) . NASA's Mars Atmosphere and Volatile Evolution (Maven for short) and India's Mangalaan Orbital Mission (MOM for short. NASA spent $671 million on Maven. India's MOM is famous in technical circles for getting to Mars for about one tenth that. Both orbiters still have one heavy duty maneuver before they can be considered to have "arrived" That is the Mars Orbit Insertion (MOI) a 34 minute burn of the rocket engines to slow the orbiter to Mars orbit velocity. That's a long burn, especially for an engine that has been floating in vacuum, unused, for nearly a year. To make the MOI dicier, the maneuver must be executed by the onboard microprocessor, since radio signals from Earth take 20 minutes to reach Mars. 15 years ago a gross software fault caused a Mars Orbiter to crash on Mars from a failure of the MOI maneuver.
Maven carries instruments to verify a Mars creation theory. Now that we have good evidence of free surface water in the distant Martian past, the theory suggests that the water vapor escaped into interplanetary space due to Mar's weak gravity. Maven's instruments will measure the flow of gases and ions in the upper Martian atmosphere, hoping to show that water is still escaping and measure the rate, as a way of figuring how long surface water lasted on Mars, before it escaped into space.
To add to the fun, Siding Spring, a comet, will swing by Mars on 19 October. It is believed that Siding Spring is a new comet, on it's first trip into the inner solar system. It is thought that new comets are chunks of ice and gravel that have been floating in interstellar space ("the Ort Cloud") since the beginning of the solar system, and Siding Spring represents matter from the dawn of time, or at least the birth of the solar system which is a long time ago. Scientists are eager for any information the Mars orbiters can gather from Siding Spring.
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