This week is an exciting time to be a Martian. On Sunday evening, the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite successfully entered orbit around Mars. Not to be outdone, this evening (tomorrow morning in Europe and Asia) the Mars Orbiter Mission (MOM) will do the same. You may be wondering why we need two send two more missions to Mars, when it’s already inhabited entirely by robots. Today let’s look at each of these missions and their scientific goals to see what we’ll learn about Mars from each of these orbiters.
MAVEN: Where’s all the water?
For more than 100 years, there have been claims of water on Mars. In 1877, an Italian astronomer named Giovanni Schiaparelli observed a series of lines on the surface of Mars, which he described as canali, or canals. Two decades later, Percival Lowell published a book describing his observations of these canals and his belief that they were built for irrigation by an advanced civilization. This claim was very controversial among the astronomers of the era, and was discredited when spectroscopic observations of Mars found no evidence for significant water vapor in its atmosphere.
Recently, the idea of water on Mars has returned, although not quite at the level Lowell believed. Data from the Mars Phoenix Lander suggest that the north polar ice cap has as much as 30% of the total water content of the Greenland ice sheet. In fact, if all the surface ice on Mars were melted, it is believed that Mars would be inundated with an ocean more than 100 feet deep! The current best estimate is that the total water content on Mars, including the water tied up in clay and other rocks, is somewhere between 6 and 27 percent of the total water content on the Earth.
There is also evidence that billions of years ago, Mars had considerably more water than it does now. Meteorites from the red planet that have landed on Earth appear to have been exposed to liquid water, while there is also geological evidence for lakes, rivers, and deltas that may have existed 2-4 billion years ago.
Now that we’re pretty sure there was water, what happened to it? This is the question that MAVEN is trying to answer. MAVEN will test the theory that Martian water was lost as the planet’s magnetic field disappeared, allowing the solar wind to push away the planet’s atmosphere and water vapor. With eight instruments, MAVEN will probe the upper atmosphere of Mars and its interaction with the solar wind over the next Earth year. Combined with observations from Curiosity from the ground, scientists will be able to project the observations backwards in time to when Mars had a significantly thicker atmosphere to understand if the solar wind is entirely responsible for the removal of Martian surface water.
MOM: A First for India
The first successful mission to Mars was Mariner 4, which reached Mars in 1965 and took 21 images during its flyby. Since then there have been many successful Mars missions—15 by NASA, 3 by the Soviet space program and 2 by the European Space Agency. Tonight, India hopes to join this list with the arrival of the Mars Orbiter Mission (MOM) to the red planet.
MOM contains five instruments which will study Mars. Three are designed to probe the upper atmosphere, while one maps the temperature of the surface of the planet and one takes images of the surface. These instruments will collect data for six months, complementing the observations taken by MAVEN and Curiousity.
While the data will be valuable, MOM’s main purpose is as a “demonstration of technology,” showing that India is quickly becoming a significant player in the field of planetary exploration. This mission comes only six years after the launch of the Chandrayaan lunar orbiter. MOM isn’t the end goal of the Indian Space Research Organization (ISRO) either: it is the beginning. If successful, ISRO plans to launch a second Mars orbiter between 2017 and 2020, this time with a larger science mission planned.
This is an exciting time for the scientists who study Mars. Opportunity is still rolling along 11 years after landing on the surface. Curiousity joined Opportunity in 2012, and there will be at least three more landers on the Martian surface in the next ten years. The addition of ISRO to the worldwide planetary science community is great for scientists both inside and outside of India. Together, MAVEN and MOM present an intriguing look at the current status of Martian exploration across the world; data from both and their successors will paint a picture of a Mars long gone, perhaps with massive oceans and a thick atmosphere.