What makes Mars red?

First image shared by UAE's Hope probe since entering the planet's orbit shows Mars looking more yellow

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The Hope probe shared its first close-up image of Mars on Sunday in what was described by local rulers as a "defining moment" in UAE history.

It was taken from an altitude of 24,700km above the Martian surface. The impressive image showed Olympus Mons, the solar system's largest volcano, at sunrise. But the Red Planet was captured looking more yellow and orange than red.

Though the image may not have shown the vibrant colour some have come to expect from Mars, it is, however, a more accurate representation of the planet's typical colour.

Named after the Roman god of war, Mars is known as the Red Planet for its rusty-coloured surface. Its surface material contains a lot of iron oxide – a heavy element found in many planets – which gives the planet its reddish hue. Iron is black until it is exposed to oxygen and becomes red iron oxide.

According to space.com, iron oxide is forged in the heart of long-dead stars and swirled around in clouds of dust and gas before accumulating into planets through gravitational collapses.

The bulk of Earth's iron sank into its core, while much of Mars' iron also remained in its upper layers, because the planet is smaller and has a weaker gravity.

Mars appears to change colour depending on how volatile its surface is. Dust storms carrying oxidised iron into its atmosphere will give the planet a redder hue. Iron oxide also absorbs blue and green wavelengths of the light spectrum, while reflecting red wavelengths.

The photo captured by Hope was taken by the Emirates eXploration imager – one of three instruments aboard the space craft – hours after it entered orbit, at 12.36am on February 10.

It is a composite of red, green and blue images taken by the imager.

The image of Mars taken by the Hope probe. Roy Cooper / The National
The image of Mars taken by the Hope probe. Roy Cooper / The National

Mars' north pole can be seen in the upper left of the image, with clouds at the very top and middle right.

Ice clouds can be seen over the southern highlands (in the lower right of the image) and the Alba Mona volcano (in the upper left).

These clouds, which can be seen in different geographic regions and different times of the day, will help the Hope probe study the atmosphere.

The picture is the first of more than 1,000 GB of Mars data that the probe will send back to Earth. All science retrieved from the mission will be freely shared with more than 200 academic and scientific institutions around the world.