Hubble Spots First Indications of Water on TRAPPIST-1s Planets

This artist’s impression shows the view from the surface of one of the planets in the TRAPPIST-1 system. A powerful laser beacon using current and near-future technology could send a signal strong enough to be detected by any alien astronomers here. Credit: NASA/ESA/HST

In February of 2017, astronomers from the European Southern Observatory (ESO) announced the discovery of seven rocky planets around the nearby star of TRAPPIST-1. Not only was this the largest number of Earth-like planets discovered in a single star system to date, the news was also bolstered by the fact that three of these planets were found to orbit within the star’s habitable zone.

Since that time, multiple studies have been conducted to ascertain the likelihood that these planets are actually habitable. Thanks to an international team of scientists who used the Hubble Space Telescope to study the system’s planets, we now have the first clues as to whether or not water (a key ingredient to life as we know it) exists on any of TRAPPIST-1s rocky worlds.

The team’s study, titled “Temporal Evolution of the High-Energy Irradiation and Water Content of TRAPPIST-1 Exoplanets“, recently appeared on the Hubble site. Led by Swiss astronomer Vincent Bourrier from the Observatoire de l’Université de Genève, the team relied on Hubble’s Space Telescope Imaging Spectrograph (STIS) to study the amount of ultraviolet radiation each of the TRAPPIST-1 planets receives.

Artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii and masses as compared to those of Earth. Credit: NASA/JPL

As Bourrier explained in a Hubble press release, this helped them to determine the water content of the system’s seven planets:

“Ultraviolet radiation is an important factor in the atmospheric evolution of planets. As in our own atmosphere, where ultraviolet sunlight breaks molecules apart, ultraviolet starlight can break water vapor in the atmospheres of exoplanets into hydrogen and oxygen.”

How ultraviolet radiation interacts with a planet’s atmosphere is important when it comes to assessing the potential habitability of a planet. Whereas lower-energy UV radiation causes photodissociation, a process where water molecules break down into oxygen and hydrogen, extreme ultraviolet rays (XUV radiation) and x-rays cause the upper atmosphere of a planet to heat up – which causes the hydrogen and oxygen to escape.

Since hydrogen is lighter than oxygen, it is more easily lost to space where its spectra can be observed. This is precisely what Bourrier and his team did. By monitoring the TRAPPIST-1 planets spectra for signs of hydrogen loss, the team was effectively able to gauge their water content. What they found was that the UV radiation emitted by TRAPPIST-1 suggests that its planets could have lost quite a lot of water during their history.

The losses were most severe for the innermost planets – TRAPPIST-1b and 1c – which receive the most UV radiation from their star. In fact, the team estimates that these planets could have lost more than 20 Earth-oceans worth of water in the course of the system’s history – which is estimated to be between 5.4 and 9.8 billion years old. In other words, these inner planets would be bone dry and most definitely sterile.

This illustration shows the seven TRAPPIST-1 planets as they might look as viewed from Earth using a fictional, incredibly powerful telescope. Credit: NASA/JPL-Caltech

However, these same findings also suggest that the outer planets of the system have lost significantly less water over time, which could mean that they still possess abundant amounts on their surfaces. This includes the three planets that are within the star’s habitable zone – TRAPPIST-1e, f and g – which indicates that these planets could be habitable after all.

These findings are bolstered by the calculated water loss and geophysical water release rates, which also favor the idea that the more-massive and outermost planets have retained most of their water over time. These findings are very significant, in that they further demonstrate that atmospheric escape and evolution are closely linked on the planets of the TRAPPIST-1 system.

The findings are also encouraging, since previous studies that considered atmospheric loss in this system painted a rather grim picture. These include those that indicated that TRAPPIST-1 experiences too much flare, that even calm red dwarfs subject their planets to intense radiation over time, and that the distance between TRAPPIST-1 and its respective planets would mean that solar wind would be deposited directly onto their atmospheres.

In other words, these studies cast doubt on whether or not stars that orbit M-type (red dwarf) stars would be able to retain their atmospheres over time – even if they had an Earth-like atmosphere and magnetosphere. Like Mars, this research indicated that atmospheric stripping caused by solar wind would inevitably render their surfaces cold, desiccated, and lifeless.

Artist’s illustration showing the difference  TRAPPIST-1 in relation to our Sun. Credit: ESO

In short, this is one of the few pieces of good news we’ve received since the existence of seven planets in the TRAPPIST-1 system (and three potentially habitable ones) was first announced. It’s also a positive indication as far as the habitability of red dwarf star systems go. In recent years, many of those impressive exoplanet finds have taken place around red dwarf stars – i.e. Proxima b, LHS 1140b, Gliese 581g, Gliese 625b, and Gliese 682c.

Given the number of rocky planets that have been detected orbiting this type of star – and the fact that they are the most common in in the Universe (accounting for 70% of stars in the Milky Way alone) – knowing that they could support habitable planets is certainly welcome! But of course, Bourrier and his colleagues emphasize that the study is not conclusive, and further research is needed to determine if any of the TRAPPIST-1 planets are actually watery.

As Bourieer indicated, this will most likely involve next-generation telescopes:

“While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability.”

Rocky planets around the most common type of star, the potential to retain water, and 1oo billion potential planets in the Milky Way Galaxy alone. One thing is for sure: the James Webb Space Telescope is going to have its hands full once it is deployed in October of 2018!

And be sure to check out this animation of the TRAPPIST-1 system as well, courtesy of L. Calçada and the ESO:

Further Reading: Hubble Space Telescope, HST (2)

Spirit Rover Landed on Mars 10 Years Ago Today

Ten Years Ago, Spirit Rover Lands on Mars
This bird’s-eye view from August 2005 combines a self-portrait of the spacecraft deck and a panoramic mosaic of the Martian surface as viewed by NASA’s Mars Exploration Rover Spirit. The rover’s solar panels are still gleaming in the sunlight, having acquired only a thin veneer of dust two years after the rover landed and commenced exploring the red planet. Spirit captured this 360-degree panorama on the summit of “Husband Hill” inside Mars’ Gusev Crater. During the period from Spirit’s Martian days, or sols, 583 to 586 (Aug. 24 to 27, 2005), the rover’s panoramic camera acquired the hundreds of individual frames for this largest panorama ever photographed by Spirit. Credit: NASA/JPL-Caltech/Cornell
See Spirit’s 1st and last panoramas and more imagery below[/caption]

Today, Jan. 3, marks the 10th anniversary since the safe landing of NASA’s renowned Spirit rover on the plains of Mars on Jan. 3, 2004.

Spirit comprises one half of NASA’s now legendary pair of Mars Exploration Rovers (MER). Opportunity, her twin sister landed, on the opposite side of the Red Planet three weeks later – on Jan. 24, 2004. The goal was to “follow the water” as a potential enabler for past Martian microbes if they ever existed.

Together, the long-lived, golf cart sized robots proved that early Mars was warm and wet, billions of years ago – a key finding in the search for habitats conducive to life beyond Earth.

Exactly a decade ago, the famous robot survived the scorching atmospheric heating of the 6 minute plunge through the thin Martian atmosphere, bounced some two dozen times cocooned inside cushioning airbags, and gradually rolled to a stop inside 100 mile wide Gusev Crater. It was known as the “6 minutes of Terror”.

The three petaled landing pad opened and Spirit was dramatically born in a milestone event that will be forever remembered in the annuls of history because of the groundbreaking scientific discoveries that ensued and the unbelievable longevity of the twins.

Ten Years Ago, Spirit Rover Lands on Mars . This mosaic image taken on Jan. 4, 2004, by the navigation camera on the Mars Exploration Rover Spirit, shows a 360 degree panoramic view of the rover on the surface of Mars.   Spirit operated for more than six years after landing in January 2004 for what was planned as a three-month mission. Credit: NASA/JPL
Ten Years Ago, Spirit Rover Lands on Mars
This mosaic image taken on Jan. 4, 2004, by the navigation camera on the Mars Exploration Rover Spirit, shows a 360 degree panoramic view of the rover on the surface of Mars. Spirit operated for more than six years after landing in January 2004 for what was planned as a three-month mission. Credit: NASA/JPL

Before they were launched atop Delta II rockets in the summer of 2003 from Cape Canaveral, the dynamic, solar powered robo duo were expected to last a mere three months – with a ‘warranty’ of 90 Martian days (Sols).

Either dust accumulation on the life giving solar panels, an engineering issue or the extremely harsh Martian environment was expected to somehow terminate them mercilessly.

In reality, both robots enormously exceeded expectations and accumulated a vast bonus time of exploration and discovery in numerous extended mission phases.

'McMurdo' Panorama from Spirit's 'Winter Haven' . This beautiful scene reveals a tremendous amount of detail in Spirit's surroundings at a place called "Winter Haven," where the rover spent many months parked on a north-facing slope in order to keep its solar panels pointed toward the sun for the winter. During this time, it captured several images to create this high resolution panorama. During that time, while the rover spent the daylight hours conducting as much scientific research as possible, science team members assigned informal names to rock outcrops, boulders, and patches of soil commemorating exploration sites in Antarctica and the southernmost islands of South America. Antarctic bases are places where researchers, like the rovers on Mars, hunker down for the winter in subzero temperatures. During the past Martian winter, Spirit endured temperatures lower than minus 100 degrees Celsius (minus 148 degrees Fahrenheit). Credit: NASA/JPL/Cornell
‘McMurdo’ Panorama from Spirit’s ‘Winter Haven’
This beautiful scene reveals a tremendous amount of detail in Spirit’s surroundings at a place called “Winter Haven,” where the rover spent many months parked on a north-facing slope in order to keep its solar panels pointed toward the sun for the winter. During this time, it captured several images to create this high resolution panorama. During that time, while the rover spent the daylight hours conducting as much scientific research as possible, science team members assigned informal names to rock outcrops, boulders, and patches of soil commemorating exploration sites in Antarctica and the southernmost islands of South America. Antarctic bases are places where researchers, like the rovers on Mars, hunker down for the winter in subzero temperatures. During the past Martian winter, Spirit endured temperatures lower than minus 100 degrees Celsius (minus 148 degrees Fahrenheit). Credit: NASA/JPL/Cornell

No one foresaw that Martian winds would occasionally clean the solar panels to give them a new lease on life or that the components would miraculously continue functioning.

Spirit endured the utterly extreme Red Planet climate for more than six years until communications ceased in 2010.

Opportunity is still roving Mars today, and doing so in rather good condition!

Altogether, Spirit drove 4.8 miles (7.73 kilometers),that’s about 12 times more than the original goal set for the mission.

She transmitted over 128,000 images.

After landing in the dusty plains, she headed for the nearby Columbia Hills some 2 miles away and ultimately became the first Martian mountaineer, when she scaled Husband Hill and found evidence for the flow of liquid water at the Hillary outcrop.

Spirit acquired this mosaic on Sol 1202  (May 21, 2007), while investigating the area east of the elevated plateau known as "Home Plate" in the "Columbia Hills." The mosaic shows an area of disturbed soil, nicknamed "Gertrude Weise" by scientists, made by Spirit's stuck right front wheel. The trench exposed a patch of nearly pure silica, with the composition of opal. It could have come from either a hot-spring environment or an environment called a fumarole, in which acidic, volcanic steam rises through cracks. Either way, its formation involved water, and on Earth, both of these types of settings teem with microbial life. Credit: NASA/JPL-Caltech/Cornell
Spirit acquired this mosaic on Sol 1202 (May 21, 2007), while investigating the area east of the elevated plateau known as “Home Plate” in the “Columbia Hills.” The mosaic shows an area of disturbed soil, nicknamed “Gertrude Weise” by scientists, made by Spirit’s stuck right front wheel. The trench exposed a patch of nearly pure silica, with the composition of opal. It could have come from either a hot-spring environment or an environment called a fumarole, in which acidic, volcanic steam rises through cracks. Either way, its formation involved water, and on Earth, both of these types of settings teem with microbial life. Credit: NASA/JPL-Caltech/Cornell

The rovers were not designed to climb hills. But eventually she scaled 30 degree inclines.

The rover was equipped with a rock grinder named the Rock Abrasion Tool (RAT) built by Honeybee Robotics.

Spirit ground the surfaces off 15 rock targets and scoured 92 targets with a brush to prepare the targets for inspection with spectrometers and a microscopic imager, according to NASA.

Eventually she drove back down the hill and made even greater scientific discoveries in the area known as ‘Home Plate’.

Spirit survived three harsh Martian winters and only succumbed to the Antarctic-like temperatures when she unexpectedly became mired in an unseen sand trap driving beside an ancient volcanic feature named ‘Home Plate’ that prevented the solar arrays from generating life giving power to safeguard critical electronic and computer components.

In 2007, Spirit made one of the key discoveries of the mission at ‘Home Plate’ when her stuck right front wheel churned up a trench of bright Martian soil that exposed a patch of nearly pure silica, which was formed in a watery hot spring or volcanic environment.

Spirit was heading towards another pair of volcanic objects named ‘von Braun’ and ‘Goddard’ and came within just a few hundred feet when she died in the sand trap.

See Spirits last panorama below – created from raw images taken in Feb. 2010 by Marco Di Lorenzo and Ken Kremer.

Last View from Spirit rover on Mars.  Spirit’s last panorama from Gusev Crater was taken during February 2010 before her death from extremely low temperatures during her 4th Martian winter.  Spirit was just 500 feet from her next science target - dubbed Von Braun – at center, with Columbia Hills as backdrop.  Mosaic Credit: Marco Di Lorenzo/ Kenneth Kremer/ NASA/JPL/Cornell University.  Mosaic featured on Astronomy Picture of the Day (APOD) on 30 May 2011 - http://apod.nasa.gov/apod/ap110530.html
Last View from Spirit rover on Mars
Spirit’s last panorama from Gusev Crater was taken during February 2010 before her death from extremely low temperatures during her 4th Martian winter. Spirit was just 500 feet from her next science target – dubbed Von Braun – at center, with Columbia Hills as backdrop. Mosaic Credit: Marco Di Lorenzo/ Kenneth Kremer/ NASA/JPL/Cornell University. Mosaic featured on Astronomy Picture of the Day (APOD) on 30 May 2011 – http://apod.nasa.gov/apod/ap110530.html

Here’s how the rovers’ principal investigator, Steve Squyres of Cornell University, Ithaca, N.Y., described some of the key findings in a NASA statement, starting with what Spirit found after driving from the crater floor where it landed into the Columbia hills to the east:

“In the Columbia Hills, we discovered compelling evidence of an ancient Mars that was a hot, wet, violent place, with volcanic explosions, hydrothermal activity, steam vents — nothing like Mars today.

“At Opportunity’s landing site, we found evidence of an early Mars that had acidic groundwater that sometimes reached the surface and evaporated away, leaving salts behind. It was an environment with liquid water, but very different from the environment that Spirit told us about.

“When Opportunity got to the rim of Endeavour Crater, we began a whole new mission. We found gypsum veins and a rich concentration of clay minerals. The clay minerals tell us about water chemistry that was neutral, instead of acidic — more favorable for microbial life, if any ever began on Mars.”

“Because of the rovers’ longevity, we essentially got four different landing sites for the price of two.”

MER10-SpiritAndOpportunity_ByTheNumbers[1]

Meanwhile, NASA’s new Curiosity rover just celebrated 500 Sols on Mars and is speeding towards Mount Sharp from inside Gale Crater – which is about the same size as Gusev crater.

And a pair of newly launched orbiters are streaking to the Red Planet; NASA’s MAVEN and India’s MOM.

And China’s new Yutu lunar rover and Chang’e-3 lander are napping through the lunar night until mid-January.

Stay tuned here for Ken’s continuing Curiosity, Chang’e-3, SpaceX, Orbital Sciences, LADEE, MAVEN, Mars rover and MOM news.

Ken Kremer

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Learn more about Curiosity, MAVEN, MOM, Mars rovers, SpaceX, Orbital Sciences Antares Jan. 8 launch, and more at Ken’s upcoming presentations

Jan 6-8: “Antares/Cygnus ISS Rocket Launch from Virginia on Jan. 8” & “Space mission updates”; Rodeway Inn, Chincoteague, VA, evening