I remember the Summer of 1997 when a shoebox-sized Mars rover literally broke the Internet.
Sojourner – the first rover we sent to another planet – had just landed on Mars in a giant space airbag bouncing along the surface to a safe stop. The Internet was new. And I was a young space enthusiast with a dial-up modem. For the first time, images from a space exploration mission were beamed to an audience that was connected online. Now we use the term “broke the Internet” as a hyperbolic phrase for various Internet phenomena, but interest in the Mars mission in 97 drove so many hits to NASA mirror servers around the world that global web traffic was disrupted. Patiently I watched as, line by line, orange sky to red stone, the first image posted by NASA loaded on my screen…it took about an hour. Each line resolved was like my own exploration of the planet. And finally, the landing site, in “real time”, was revealed to me and the entire world all at once. What would we discover together?
Remember back in 2008 when the Phoenix lander on Mars scraped away a few inches of rust-colored regolith to reveal water ice? Or in 2009, when Mars Reconnaissance Orbiter observations revealed vast areas of subsurface ice, event at low latitudes?
These findings – and many more like them – indicate there’s a lot of interesting things going on underneath Mars’ lifeless surface. Since we know from experience on Earth that anywhere there is water, there is life, the question of life on – or under – Mars’s surface is always provocative.
An artist's illustration of the ExoMars/Rosalind Franklin rover on Mars. Image Credit: ESA/ATG medialab
We all know how exploration by rover works. The rover is directed to a location and told to take a sample. Then it subjects that sample to analysis and sends home the results. It’s been remarkably effective.
But it’s expensive and time-consuming to send all this data home. Will this way of doing things still work? Or can it be automated?
In the course of studying Mars, scientists have come to identify some key similarities to Earth’s own. One notable example is the way our atmospheres interact with sunlight to produce dazzling displays of energy. On Earth, these include not just the aurorae near the polar regions (Aurora Borealis and Australis), but the constant green glow that is the result of oxygen molecules interacting with sunlight (aka. “airglow”).
On Earth, airglow can be seen “edge-on” from space, as exemplified by the many spectacular images that are taken by astronauts aboard the International Space Station (ISS). This phenomenon was recently observed around Mars for the first time by the ESA’s Trace Gas Orbiter (TGO), which arrived at Mars in 2016 a part of the ExoMars program. Like aurorae, this observation is yet another example of how Mars is “Earth’s Twin.”
On October 19th, 2016, the NASA/ESA ExoMars mission arrived at the Red Planet to begin its study of the surface and atmosphere. While the Trace Gas Orbiter (TGO) successfully established orbit around Mars, the Schiaparelli Lander crashed on its way to the surface. At the time, the Mars Reconnaissance Orbiter (MRO) acquired images of the crash site using its High Resolution Imaging Science Experiment (HiRISE) camera.
In March and December of 2019, the HiRISE camera captured images of this region once again to see what the crash site looked like roughly three years later. The two images show the impact crater that resulted from the crash, which was partially-obscured by dust clouds created by the recent planet-wide dust storm. This storm lasted throughout the summer of 2019 and coincided with Spring in Mars’ northern hemisphere.
This artist's rendition depicts NASA's Mars 2020 rover studying its surroundings. Credit: NASA
NASA’s Mars 2020 Rover is heading to Mars soon to look for fossils. The ESA/Roscosmos ExoMars rover is heading to Mars in the same time-frame to carry out its own investigations into Martian habitability. To meet their mission objectives, the scientists working the missions will need to look at a lot of rocks and uncover and understand the clues those rocks hold.
To help those scientists prepare for the daunting task of analyzing and understanding Martian rocks from 160 million km (100 million miles) away, they’ve gone on a field trip to Australia to study stromatolites.
During winter in the polar regions, a thin layer of carbon dioxide ice covers the surface and then sublimates – turns directly from ice into vapour – with the first light of spring. In the dune fields, this springtime defrosting occurs from the bottom up, trapping gas between the ice and the sand. As the ice cracks, this gas is released violently and carries sand with it, forming the dark patches and streaks observed in this CaSSIS image. ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO
Springtime on Earth can be a riotous affair, as plants come back to life and creatures large and small get ready to mate. Nothing like that happens on Mars, of course. But even on a cold world like Mars, springtime brings changes, though you have to look a little more closely to see them.
Lucky for us, there are spacecraft orbiting Mars with high-resolution cameras, and we can track the onset of Martian springtime through images.
Trace Gas Orbiter, Schiaparelli and the ExoMars rover at Mars. Credit: ESA/ATG medialab
Next year, the European Space Agency (ESA) will be sending the ExoMars 2020 mission to the Red Planet. This mission consists of an ESA-built rover (Rosalind Franklin) and a Russian-led surface science platform (Kazachok) that will study the Martian environment in order to characterize its surface, atmosphere, and determine whether or not life could have once existed on the planet.
In preparation for this mission, engineers are putting the rover and lander through their paces. This includes the ongoing development of the mission’s parachute system, which is currently in troubleshooting after a failed deployment test earlier this month. These efforts are taking place at the Swedish Space Corporation testing site in Esrange, and involve the largest parachute ever used by a mission to Mars.
The Trace Gas Orbiter arrived at Mars in 2016. Credit: ESA
In 2003, scientists from NASA’s Goddard Space Center made the first-ever detection of trace amounts of methane in Mars’ atmosphere, a find which was confirmed a year later by the ESA’s Mars Express orbiter. In December of 2014, the Curiosity rover detected a tenfold spike of methane at the base of Mount Sharp, and later uncovered evidence that Mars has a seasonal methane cycle, where levels peak in the late northern summer.
Since it’s discovery, the existence of methane on Mars has been considered one of the strongest lines of evidence for the existence of past or present life. So it was quite the downer last week (on Dec. 12th) when the science team behind one of the ESA’s ExoMars Trace Gas Orbiter (TGO) spectrometers announced that they had found no traces of methane in Mars’ atmosphere.
Mars’ south polar ice cap. Credit: ESA / DLR / FU Berlin /
According to evidence gathered by multiple robotic orbiters, rovers, and landers over the course of several decades, scientists understand that Mars was once a warmer, watery place. But between 4.2 and 3.7 billion years ago, this began to change. As Mars magnetic field disappeared, the atmosphere slowly began to be stripped away by solar wind, leaving the surface the cold and dry and making it impossible for water to exist in liquid form.
While much of the planet’s water is now concentrated in the polar ice caps, scientists have speculated some of Mars’ past water could still be located underground. Thanks to a new study by a team of Italian scientists, it has now been confirmed that liquid water still exists beneath Mars’ southern polar region. This discovery has put an end to a fifteen-year mystery and bolstered the potential for future missions to Mars.
Radar detection of water under the south pole of Mars. Credit: ESA/NASA/JPL/ASI/Univ. Rome
So far, robotic missions have revealed considerable evidence of past water on Mars. These include dried-out river valleys and gigantic outflow channels discovered by orbiters, and evidence of mineral-rich soils that can only form in the presence of liquid water by rovers and landers. Early evidence from the ESA’s Mars Express probe has also showed that water-ice exists at the planet’s poles and is buried in the layers interspersed with dust.
However, scientists have long suspected that liquid water could exist beneath the polar ice caps, much in the same way that liquid water is believed to underlie glaciers here on Earth. In addition, the presence of salts on Mars could further reduce the melting point of subsurface water and keep it in a liquid state, despite the sub-zero temperatures present on both the surface and underground.
For many years, data from the Mars Express’Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument – which has been used to study the southern polar region – has remained inconclusive. Like all ground-penetrating radar, this instrument relies on radar pulses to map surface topography and determine the properties of the materials that lie beneath the surface.
Luckily, after considerable analysis, the study team was able to develop new techniques that allowed them to collect enough high-resolution data to confirm the presence of liquid water beneath the southern ice cap. As Andrea Cicchetti, the MARSIS operations manager and a co-author on the new paper, indicated:
“We’d seen hints of interesting subsurface features for years but we couldn’t reproduce the result from orbit to orbit, because the sampling rates and resolution of our data was previously too low. We had to come up with a new operating mode to bypass some onboard processing and trigger a higher sampling rate and thus improve the resolution of the footprint of our dataset: now we see things that simply were not possible before.”
Water detection under the south pole of Mars. Credit: Context map: NASA/Viking; THEMIS background: NASA/JPL-Caltech/Arizona State University; MARSIS data: ESA/NASA/JPL/ASI/Univ. Rome; R. Orosei et al 2018
What they found was that the southern polar region is made of many layers of ice and dust down to a depth of about 1.5 km over a 200 km-wide area, and featured an anomalous area measuring 20-km wide. As Roberto Orosei, the principal investigator of the MARSIS experiment and lead author of the paper, explained in a recent ESA press release:
“This subsurface anomaly on Mars has radar properties matching water or water-rich sediments. This is just one small study area; it is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered.”
After analyzing the properties of the reflected radar signals and taking into account the composition of the layered deposits and expected temperature profiles below the surface, the scientists concluded that the 20-km wide feature is an interface between the ice and a stable body of liquid water. For MARSIS to be able to detect such a patch of water, it would need to be at least several tens of centimeters thick.
These findings also raise the possibility of there being life on Mars, both now and in the past. This is based on research that found microbial life in Lake Vostok, which is located some 4 km (2.5 mi) below the ice in Antarctica. If life can thrive in salty, subglacial environments on Earth, then it is possible that they could survive on Mars as well. Determining if this is the case will be the purpose of existing and future missions to Mars.
The MARSIS instrument on the Mars Express is a ground penetrating radar sounder used to look for subsurface water and ice. Credit: ESA
As Dmitri Titov, one of the Mars Express project scientist, explained:
“The long duration of Mars Express, and the exhausting effort made by the radar team to overcome many analytical challenges, enabled this much-awaited result, demonstrating that the mission and its payload still have a great science potential. This thrilling discovery is a highlight for planetary science and will contribute to our understanding of the evolution of Mars, the history of water on our neighbour planet and its habitability.”
The Mars Express launched on June 2nd, 2003, and will celebrate 15 years in orbit of Mars by December 25th this year. In the coming years, it will be joined by the ESA’s ExoMars 2020 mission, NASA’s Mars 2020 Rover, and a number of other scientific experiments. These missions will pave the way for a potential crewed mission, which NASA is planning to mount by the 2030s.
If there is indeed liquid water to be found on Mars, it will go a long way towards facilitating future research and even an ongoing human presence on the surface. And if there is still life on Mars, the careful research of its ecosystems will help address the all-important question of how and when life emerged in the Solar System.
