In May 2015, Smithsonian Magazine reported that five operational satellites from three different space agencies were orbiting Mars, collecting an array of information.
Three of those satellites—the Mars Global Surveyor, Mars Odyssey, and the Mars Reconnaissance Orbiter—have been ascertaining information about Mars’ gravity field for over a decade. Now, NASA has compiled the most detailed gravitational map of the Red Planet to date.
The research was published in early March by the science journal Icarus.
According to study co-author Antonio Genova, gravity maps are akin to a doctor using an X-ray machine on a patient, providing a glimpse of a planet’s interior. Understanding the gravity field can help scientists understand the planet’s geographic past, and can help future spacecraft navigate the planet’s orbit more easily.
In order to map the gravity field, the researchers pooled together 16 years of data, which was continuously collected while the spacecrafts were in orbit around Mars. This planet’s surface, being uneven, exerts different gravitational pulls. For example, a spacecraft passing over Olympus Mons, the tallest peak in the solar system at 21,230 m, would feel a greater gravitational pull than a spacecraft traveling over a canyon.
All the data was relayed to NASA’s Deep Space Network.
However, the researchers also had to account for other effects on the spacecraft that might manifest as gravitational changes, including sunlight on the spacecraft’s solar panels and the drag from Mars’ upper atmosphere. These extraneous effects were removed over a two-year period.
“With this new map, we’ve been able to see gravity anomalies as small as about 100 km across, and we’ve determined the crustal thickness of Mars with a resolution around 120 km,” said Genova in a statement. “The better resolution of the new map helps interpret how the crust of the planet changed over Mars’ history in many regions.”
Additionally, the researchers were able to observe how gravity changed over the planet’s solar cycle, which lasts 11 years. The team discovered that roughly 4 trillion tons of carbon dioxide cycles between the planet’s poles annually. The shift occurs during a hemisphere’s winter. The carbon dioxide freezes out from the atmosphere to either the north or south pole.
Further, they confirmed the presence of Mars’ liquid outer core, and observed the tides in the planet’s crust and mantle, which is caused by the sun and Mars’ moons Phobos and Deimos.
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