Mars is the fourth terrestrial (or rocky) planet from the sun and Earth's closest planetary neighbor, at an average distance of 225 million kilometers. It is about half the size of Earth, contains a fraction of its atmosphere, and has two irregularly shaped moons: Phobos and Deimos.
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It formed over millions of years as small clumps of matter orbiting the sun smashed together, solidified, and cooled. Geological features indicate the presence of past surface water, which evaporated away due to the planet's weak gravitational field.
A single day on Mars lasts 24.6 hours, while a year lasts 687 Earth days. The rusting of iron in rocks on the Martian surface contributes to brown, gold, and tan colorations.
The twin machines were tasked with studying the geology of Mars to identify evidence of past water activity, determine the composition of minerals, rocks, and soils, and perform "ground truth" experiments to calibrate and validate observations made by Mars orbiters.
NASA has studied Mars extensively over 60 years using telescopes, orbiters, and rovers. From April 2021 to January 24, the Ingenuity helicopter completed its technology demonstration objective by flying more than 17 kilometers above the Martian surface.
Scientists believe that over hundreds of millions of years, energetic particles from the sun colliding with atmospheric particles, flinging them away from Mars' weak gravitational field like colliding billiard balls. As atmospheric pressure decline, water also evaporated away from the surface.
The yellows spots scattered across the map indicate meteor impacts while the red regions represent volcanoes and their associated lava flows. The varying shades of brown indicate cratered highlands and midlands, which make up most of the southern hemisphere.
Images from orbiters, landers, and rovers show that Mars has a mix of surface colors resulting from variations in the mineral compositions of different regions. The reddish tint when viewed from Earth comes from kicked up particles of rusted iron.
Unlike Earth, Mars lacks geological activity and oceans, though geological evidence suggests they both existed in the past. Its northern regions have far fewer craters than the southern ones, indicating that the rock in the north formed more recently.
Sending humans to Mars in the following decades poses significant challenges, from the vast distance covered to get materials there to powering technology during weekslong dust storms. Research is ongoing to develop life support systems that can regenerate or recycle consumables.
A network of interconnected, airtight bubbles would require several orders of magnitude fewer materials than those required to re-establish the entire planet's atmosphere to resemble Earth. However, the whole network would be compromised by a single micrometeor impact that destroys the air seal.
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