For decades, robotic missions have been exploring Mars to learn more about the planet’s geological and environmental history. Next year, the Perseverance rover will join in the hunt and be the first mission to send samples back to Earth and by the 2030s, the first crewed mission is expected to take place. All of these efforts are part of an ongoing effort to find evidence of past (and maybe even present) life on Mars.
According to a new study from Rutgers University-New Brunswick., the most likely place to find this evidence is located several kilometers beneath the surface. It is here (they argue) that water still exists in liquid form, which is likely the result of geothermal heating melting thick subsurface sheets of ice. This research could help resolve lingering questions like the faint young Sun paradox.
Modern astronomy and space exploration has blessed us with a plethora of wonderful images. Whether they were images of distant planets, stars and galaxies taken by Earth-based telescopes, or close-ups of planets or moons in our own Solar System by spacecraft, there has been no shortage of inspiring pictures. But what would it look like to behold planet Earth from another celestial body?
We all remember the breathtaking photos taken by the Apollo astronauts that showed what Earth looked like from the Moon. But what about our next exploration destination, Mars? With all the robotic missions on or in orbit around the Red Planet, you’d think that there would have been a few occasions where they got a good look back at Earth. Well, as it turn out, they did!
Pictures from Space:
Pictures of Earth have been taken by both orbital missions and surface missions to Mars. The earliest orbiters, which were part of the Soviet Mars and NASA Mariner programs, began arriving in orbit around Mars by 1971. NASA’s Mariner 9 probe was the first to establish orbit around the planet’s (on Nov. 14, 1971), and was also the first spacecraft to orbit another planet.
The first orbiter to capture a picture of Earth from Mars, however, was the Mars Global Surveyor, which launched in Nov. 7th, 1996, and arrived in orbit around the planet on Sept. 12th, 1997. In the picture (shown above), which was taken in 2003, we see Earth and the Moon appearing closely together.
At the time the picture was taken, the distance between Mars and Earth was 139.19 million km (86.49 million mi; 0.9304 AU) while the distance between Mars and the Moon was 139.58 million km (86.73 million mi; 0.9330 AU). Interestingly enough, this is what an observer would see from the surface of Mars using a telescope, whereas a naked-eye observer would simply see a single point of light.
Usually, the Earth and Moon are visible as two separate points of light, but at this point in the Moon’s orbit they were too close to resolve with the naked eye from Mars. If you look closely at Earth, you can just make out the shape of South America.
The picture above was snapped by the Mars Express’s High Resolution Stereo Camera (HRSC) on the ESA’s Mars Express probe. It was also taken in 2003, and is similar in that it shows the Earth and Moon together. However, in this image, we see the two bodies at different points in their orbit – which is why the Moon looks like its farther away. Interestingly enough, this image was actually part of the first data sets to be sent by the spacecraft.
The next orbiter to capture an image of Earth from Mars was the Mars Reconnaissance Orbiter (MRO), which was launched in August of 2005 and attained Martian orbit on March 10th, 2006. When the probe reached Mars, it joined five other active spacecraft that were either in orbit or on the surface, which set a record for the most operational spacecraft in the vicinity of Mars at the same time.
In the course of its mission – which was to study Mars’ surface and weather conditions, as well as scout potential landing sites – the orbiter took many interesting pictures. The one below was taken on Oct. 3rd, 2007, which showed the Earth and the Moon in the same frame.
Pictures from the Surface:
As noted already, pictures of Earth have also been taken by robotic missions to the surface of Mars. This has been the case for as long as space agencies have been sending rovers or landers that came equipped with mobile cameras. The earliest rovers to reach the surface – Mars 2 and Mars 3– were both sent by the Soviets.
However, it was not until early March of 2004, while taking photographs of the Martian sky, that the Spirit rover became the first to snap a picture of Earth from the surface of another planet. This image was caught while the rover was attempting to observe Mars’ moon Deimos making a transit of the Sun (i.e. a partial eclipse).
This is something which happens quite often given the moon’s orbital period of about 30 hours. However, on this occasion, the rover managed to also capture a picture of distant Earth, which appeared as little more than a particularly bright star in the night sky.
The next rover to snap an image of Earth from the Martian surface was Curiosity, which began sending back many breathtaking photos even before it landed on Aug. 6th, 2012. And on Jan. 31st, 2014 – almost a year and a half into its mission – the rover managed to capture an image of both Earth and the Moon in the night sky.
In the image (seen below), Earth and the Moon are just visible as tiny dots to the naked eye – hence the inset that shows them blown up for greater clarity. The distance between Earth and Mars when Curiosity took the photo was about 160 million km (99 million mi).
Earth has been photographed from Mars several times now over the course of the past few decades. Each picture has been a reminder of just how far we’ve come as a species. It also provides us with a preview of what future generations may see when looking out their cabin window, or up at the night sky from other planets.
A digital terrain model of a portion of Mars’ Valles Marineris, the largest canyon in the Solar System. Credit: ESA/DLR/FU Berlin (G. Neukum)
Anyone who’s visited the Grand Canyon in Arizona can attest to its beauty, magnificence and sheer sense of awe that comes upon approaching its rim, whether for the first time or hundred-and-first. “Grand” almost seems too inferior a title for such an enormous geological feature — yet there’s a canyon much, much bigger stretching across the surface of Mars, one that could easily swallow all of our Grand Canyon within one of its side gullies.
The image above, released online for the first time today by ESA, is a digital terrain model of a portion of Mars’ Valles Marineris: our Solar System’s grandest canyon. It’s easy to fall into hyperbole when describing Valles Marineris. Named for NASA’s Mariner 9 spacecraft, which became the first spacecraft to orbit Mars on November 14, 1971, the canyon is over 4000 km long, 200 km wide, and 10 km deep (2,480 x 125 x 6 miles) — that’s five times deeper than the Grand Canyon and long enough to stretch across the entire contiguous United States! It’s a rift unparalleled on any other world in the Solar System.
Valles Marineris is thought to be the result of the formation of the nearby Tharsis volcanic region, home to Olympus Mons, the Solar System’s largest volcano. As the region swelled with magma billions of years ago the planet’s crust stretched and split, collapsing into a vast, deep canyon.
Much later, landslides and flowing water would help erode the canyon’s steep walls and carve out meandering side channels.
The 45-degree view above was was made from data acquired during 20 individual orbits of ESA’s Mars Express. It is presented in near-true color with four times vertical exaggeration (to increase relief contrast.) Download a high-res JPEG version here.
The largest portion of the canyon seen crossing left to right is known as Melas Chasma. Candor Chasma is the connecting trough to the north, and Hebes Chasma is in the far top left.
Below is a video released by JPL in 2006 showing a virtual fly-through of Valles Marineris, shown as if you were on a Grand Canyon-style helicopter sightseeing tour (that is, if helicopters could even work in the thin Martian air!)
Hopefully someday we’ll be seeing actual videos taken above Valles Marineris and photos captured from its rim… perhaps even by human explorers! (Please exit through the gift shop.)
Image source: ESA. Video by Eric M. De Jong and Phil Christiansen et. al, Arizona State University.