Map of Mars lets you ‘see the whole planet at once’ – 04/18/2023 – Science

A new global map of Mars offers a new perspective on the planet.

Released earlier this month, the map was assembled from 3,000 photos taken by the Hope probe, from the United Arab Emirates, and shows the red planet in its true light.

“All these colors are natural on Mars,” said Dimitra Atri, a research scientist at the Space Science Center at New York University in Abu Dhabi.

The main scientific objective of Hope, which orbited Mars just over two years ago, is to study how dust storms and other near-surface weather conditions affect the speed at which Martian air leaks into outer space.

But the orbiter also carries a camera.

When Atri saw the first image uploaded by Hope, he was “impressed with the quality of the image showing the entire disk,” he said. “I had never seen Mars like this.”

Maps of Mars are nothing new. In the 1890s, American businessman Percival Lowell used his wealth to build the Lowell Observatory in Flagstaff, Arizona, and while looking at Mars through a 24-inch telescope he spotted what he thought were artificial canals built by a Martian civilization. (He observed lightning-like structures on Venus; it was later shown that he may have inadvertently turned his telescope into a mirror and looked at the back of the eyeball itself.)

In the Space age, numerous spacecraft have passed by Mars or entered orbit around the planet.

But previous orbiters such as NASA’s Mars Global Surveyor and Mars Reconnaissance Orbiter have generally come much closer to the Martian surface, often in orbits designed to repeatedly pass above a given location at the same time of day. These images provided increasingly sharper details of the surface, including sand dunes, ravines and rocks that rolled down the hills.

“These are incredible, spectacular images,” said Atri. “But you don’t see the entire planet at once.” The lighting conditions, varying according to the place, made it difficult to create a unique and global vision.

Lighting conditions are not an issue for other types of maps. Global Surveyor carried an altimeter that projected a laser beam onto the surface. By measuring the time it took for the pulse of light to reach the surface and back, the instrument was able to measure the height of every corner of the surface. Scientists used the data to make a detailed topographic map.

For views in visible light, the Hubble Space Telescope, in orbit around Earth, can see an entire side of Mars. Scientists have assembled many of these images into a global map similar to the new map on the spacecraft Hope.

But Mars, at its closest point, is nearly 55 million km from Earth, so the Hubble images lack sharpness. Hope travels around Mars in an elliptical orbit ranging from 20,000 km to 43,000 km from the Martian surface. That’s considerably higher than the Mars Reconnaissance Orbiter, but much closer than Hubble.

“We thought: okay, we should have an atlas, because we will be able to photograph Mars over a period of several years,” said Atri. “So we must first have an atlas where we not only map the entire planet, but show how it changes over the Martian year.”

Atri was able to find images with similar lighting conditions to stitch together, omitting those where clouds obscured the surface. The process took months. “It’s extremely difficult to remove all the limits and stuff,” he said.

Atri said he and his colleagues are writing a scientific paper to describe the algorithm they developed. The same method can be applied to other spacecraft visiting other worlds, including the European Space Agency’s Jupiter Icy Moons Explorer, or Juice, launched on Friday (14).

“These icy moons look so beautiful,” said Atri. “So we should be able to apply the same technique.”

^{Translated by Luiz Roberto M. Gonçalves}