JAMES WEBB observed MARS for the first time: What have we discovered?
The best telescope
ever built by humans, conceived and designed to collect light from the most distant objects in
the universe, to look for signatures of life in the atmosphere of planets around other stars,
to give us access to a new detailed view of the cosmos, was used some days ago to observe Mars.
It seems like a waste of time and money, huh? I mean, why do we need JWST’s observations of
Mars, when we have probes orbiting around the Red planet, and robots walking on its surface?
Well, as always, science is about creativity and deep thinking.
Follow me in this video, and I’ll show you the JWST found observing Mars in infrared light.
This story starts on Sept. 19, 2022, and takes place at the so-called Palacio
de Congresos de Granada, in Spain. The Europlanet Science congress 2022
took place there, from Sept 18 to Sept 23. The meeting was meant to provide a platform
to exchange and present results, develop new ideas, and network amongst the owrldwide
planetary science community. Six days of posters, workshops, and talks intended to
provide a stimulating environment for the astrophysical community to meet.
On the second day,
the James Webb Space Telescope’s delegation released the first images and spectra of Mars.
The images and measurements were made on Sept. 5 2022 from JWST’s position,
around a million miles away from Mars. From this exclusive vantage point, JWST observes
a portion of the hemisphere of Mars illuminated by the Sun, the one facing the telescope.
It is thus able to acquire images and spectra with the spectral resolution necessary to
study short-term phenomena such as dust storms, meteorological events, and seasonal changes,
and can detect, in a single observation, processes that occur at different times of a Martian day.
The telescope observed this side of the planet and captured images
using Webb's Near-Infrared Camera (NIRCam).
In principle, such images and spectra could provide planetary scientists with a unique view
of Earth's close neighbor, delivering data that can be used in conjunction
with observations made by rovers like NASA's Perseverance and craft in the Martian orbit.
Now, there are countless iconic shots of the Red planet taken by telescopes on Earth,
by the rovers on its surface, or by the Hubble space telescope.
(To the video maker: show some of these images all over the years)
Yet every new image of the Martian globe always arouses a certain curiosity. Especially if
it is photographed by the new cool kid of astronomy, the phantasmagoric Jwst , who,
with his large infrared eye, scans the distant universe but also our cosmic neighborhood.
It's actually somewhat tricky for JWST to image something close to home.
You have to keep in mind that this is the most powerful telescope ever launched into space,
designed to be sensitive enough to detect the extraordinarily dim light from the most
distant objects in the Universe. Compared to these, Mars blazes like a furnace. So
astronomers and engineers had to come up with a plan not to over-saturate the observations.
Saturation is a phenomenon that occurs when your telescope collects too much
light and doesn’t know where to store it anymore. Saturation problems can also affect our selfies:
one has to find the right position to take it, otherwise, the picture will be
over-saturated by the light coming from the sun. Mars is bright because it reflects the light
coming from the Sun. To avoid the oversaturation that would usually result from this brightness
of Mars, the scientists taking the observations and processing the data had to employ techniques
to compensate. The timing of the exposures was incredibly short, and data analysis was
adjusted accordingly. This was the result:
In this spectacular image, we can appreciate a lot of things.
To the left, a simulated Mars globe shows the features visible to JWST:
at the top right, the image at the wavelength of 2.1 microns shows surface features such as
craters and dust. At the bottom right, the 4.3-micron image shows a heat map of
the Mars atmosphere, warmed by the Sun. Different colors indicate different temperatures
on the surface.
At 4.3 microns, as you can see, the image is dominated by thermal radiation from the
Martian atmosphere, the brightest where the Sun is almost directly in line with the planet. This is
generally where a planetary atmosphere is warmest. But heat isn't the only source of infrared light
at this wavelength. A dark smear can be seen towards the bottom right of the brightest region
in this wavelength; this is actually produced by a feature on the surface of Mars. It's a
huge impact basin called Hellas Planitia – it's one of the largest craters on Mars,
and the entire Solar System.
What we know about this basin s that it is about 7,152 km deep, and extends
for about 2,300 km from East to West. It is located in the southern hemisphere,
and it dates back to the period of intense late bombardment, between 4.1 and 3.8 billion years
ago and therefore at the initial stages of the existence of Mars. The passage of time
has degraded the entire structure marked by numerous minor craters, filled with lava flows
and shaped by atmospheric agents. However, the northern edge of the mountain range formed by the
impact is still visible, while entire areas of the northeastern and southwestern edges are missing.
(TOPOGRAPHIC MAP OF THE BASIN)
This observation might not seem that interesting, but remember to always put everything in a more
general context: for instance, the atmosphere of Mars could be changing,
and various observations – let’s say in the period of ten years from now, one observation per
year – could give us various insights on how it is changing. In 10 years, we might have snapshots of
a region of Mars, captured when a storm is going on, and another one, of the same exact region,
when Mars is quiet and there’s no storm. In this way, we would have precious information about the
Red Planet and its climate.
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As we’ve already said, James Webb also took spectra of the Red planet’s atmosphere. And
this is perhaps the most interesting part because studying the atmosphere of
Mars with great precision could help us understand the more distant exoplanets,
where other forms of life could be hiding. And we can’t wait to find them!
We measured the composition of the atmosphere of Mars.
For instance, James Webb found traces of CO2. This is nothing special, I mean,
we already know a lot about the atmosphere of the Red Planet, but Webb also found Argon traces,
and…last but not least…water, in the form of water vapor, which is what clouds on Earth are made of.
Here it is. This is Webb’s first near-infrared
spectrum of Mars, and it was captured by the Near-Infrared Spectrograph (NIRSpec).
Whereas the Mars images show differences in brightness integrated over a large number
of wavelengths from place to place across the planet at a particular day and time,
the spectrum shows the subtle variations in brightness between hundreds of different
wavelengths representative of the planet as a whole. The so-called
absorption lines give us insights into the atmosphere of the planet. As you can see,
there’s a strong absorption line in correspondence of the CO2, H2O, and CO, the carbon monoxide.
What’s really relevant about Webb’s spectrum is that it can be used to calibrate the telescope,
to reduce errors. In fact, we already know the percentage of water in the atmosphere of mars,
or the quantity of carbon dioxide: these measures come from other instruments and other probes,
and they are therefore independent measurements. In this way, we can calibrate our errors,
for instance, when it comes to exoplanets. Let’s say we confirmed the presence of liquid water on
Mars. If we ever found an exoplanet with the same water absorption lines as Mars, thanks to
the James Webb telescope, we could be 99% sure that exoplanet is also home to liquid water,
even if we would never be able to actually land on that planet to confirm it.
Or maybe we could find traces of Methane and Cyanide in the atmosphere of Mars itself.
These are really interesting molecules because they could be connected to vulcanic and geological
activity on the Red Planet, or, maybe, the presence of life. It seems that some probes
detected small traces of methane on Mars, but scientists were never able to observe them again.
Maybe their detection in the spectra of JWST could unlock a new level in our
understanding of life as we know it. In the coming weeks, the team will
concentrate on the study of spectra, trying, together with the Space Telescope Science
Institute team, to calibrate the data and fully understand their potential.
They will concentrate in the region around 3.5-3.7 microns where we will try to identify
the presence of organic molecules or to provide stringent upper limits to their concentration.
They will study and map the hydrochloric acid, which was recently discovered in the Martian
atmosphere by the spectrometers aboard the ExoMars mission, and they will try to search for methane,
the presence of which has long been debated in the scientific community.
However, this is not the
first spectrum taken by Webb. It already amazed us with the spectrum of WASP-96 b some weeks ago.
This spectrum covers a remarkably wide range of wavelengths, including visible
red light and a portion of the spectrum that has not previously been accessible
from other telescopes, for example, a part of the spectrum that is particularly sensitive
to water as well as other key molecules like oxygen, methane, and carbon dioxide,
which are not immediately obvious in the WASP-96 b spectrum but which should be detectable in other
exoplanets planned for observation by Webb. Researchers could use these observations to
assess how thick is the atmosphere of the planet, as well as how, when, and where it formed.
Welcome to a new era, the James Webb Space Telescope Era!
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