Does Proxima Centauri Create an Environment Too Horrifying for Life?

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Artist’s impression of the exoplanet Proxima Centauri b. (ESO/M. Kornmesser)

 

In 2016, the La Silla Observatory in Chile spotted evidence of possibly the most eagerly anticipated exoplanet in the Galaxy. It was a world orbiting the nearest star to the sun, Proxima Centauri, making this our closest possible exoplanet neighbour. Moreover, the planet might even be rocky and temperate.

Proxima Centauri b had been discovered by discerning a periodic wobble in the motion of the star. This revealed a planet with a minimum mass 30% larger than the Earth and an orbital period of 11.2 days. Around our sun, this would be a baking hot world.

But Proxima Centauri is a dim red dwarf star and bathes its closely orbiting planet in a level of radiation similar to that received by the Earth. If the true mass of the planet was close to the measured minimum mass, this meant Proxima Centauri b would likely be a rocky world orbiting within the habitable zone.

 

Comparison of the orbit of Proxima Centauri  b with the same region of the solar system. Proxima Centauri is smaller and cooler than the sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone. (ESO/M. Kornmesser/G. Coleman.)

Sitting 4.2 light years from our sun, a journey to Proxima Centauri b is still prohibitively long.

But as our nearest neighbor, the exoplanet is a prime target for the upcoming generation of telescopes that will attempt to directly image small worlds. Its existence was also inspiration for privately funded projects to develop faster space travel for interstellar distances.

Yet observations taken around the same time as the La Silla Observatory discovery were painting a very different picture of Proxima Centauri. It was a star with issues.

This set of observations were taken with Evryscope; an array of small telescopes that was watching stars in the southern hemisphere. What Evryscope spotted was a flare from Proxima Centauri that was so bright that the dim red dwarf star became briefly visible to the naked eye.

Flares are the sudden brightening in the atmosphere of a star that release a strong burst of energy. They are often accompanied by a large expulsion of plasma from the star known as a “coronal mass ejection”. Flares from the sun are typically between 1027 – 1032 erg of energy, released in a few tens of minutes.

For comparison, a hydrogen bomb releases the equivalent of about 10 megatons of TNT or a mere 4 x 1023 erg. Hitting the Earth, energy from solar flares and coronal mass ejections can disrupt communication equipment and create a spectacular aurora.

A solar flare erupting from the right side of the sun. (NASA/SDO)

But the Proxima super-flare spotted by Evryscope was well beyond a regular stellar flare.

On March 18 in 2016, this tiny red dwarf emitted an energy belch of 1033.5 erg. The flare consisted of one major event and three weaker ones and lasted approximately one hour, during which time Proxima Centauri became 68 times brighter.

A sudden, colossal increase in the brightness of a star does not bode well for any closely orbiting planets.

However, such a major flare might well be rare. If the star was normally fairly quiet, perhaps a planet could recover from a single very disruptive flare in the same way the Earth has survived mass extinction events.

Led by graduate student Ward Howard at the University of North Carolina, Chapel Hill, the discovering team used Evryscope to monitor Proxima Centauri for flares for a total of 1344 hours between January 2016 and March 2018. What they found was a horrifying environment, as reported in The Astrophysical Journal Letters.

While an event on the scale of the Proxima super-flare was only seen once, 24 large eruptions were spotted from the red dwarf, with energies from 1030.5 to 1032.4 erg. Allowing for the fact the star had only been observed for a small part of the year, this pattern of energy outbursts meant that a massive super-flare (1033 erg) was likely to occur at least five times annually.

 

Artist’s impression of the surface of the planet Proxima Centauri b. But what would conditions be like so close to a flaring star? (ESO/M. Kornmesser)

 

But how important is this for the planet?

The Earth is protected from flares from our sun by our atmosphere. The ozone layer absorbs harmful ultraviolet radiation with wavelengths between about 2400 – 2800 Angstroms (10-10 m), preventing it reaching the surface. So what if Proxima Centauri b had a similar protective layer of gases as the Earth?

To answer this question, Howard and his team ran simulations of an Earth-like atmosphere on Proxima Centauri b.

As is the case for the sun, the team assumed that large flares would be frequently accompanied by a coronal mass ejection. Radiation and stellar material then flooded over an Earth-like Proxima Centauri b at the observed rate. And the atmosphere crumbled.

 

Ward Howard, astrophysicist at the University of North Carolina.

High energy particles in the coronal mass ejections split the nitrogen molecules (N2) in the atmosphere, which reacted with the ozone (O3) to form nitrogen oxide (NO2). After just 5 years, 90% of the ozone in the atmosphere was lost and the amount was still decreasing.

Without ozone, the surface of Proxima Centauri b would be stripped of its protection from UV radiation. During the Proxima super-flare, the radiation dose without the protective ozone would be 65 times larger than that needed to kill 90% of one of the most UV-resilient organisms on Earth.

“Life would have to undergo extreme adaptation to UV or exist underground or underwater,” Howard notes. “Only the most resistant organisms could survive on the surface in this environment.”

The simulation does assume that Proxima Centauri b does not have a magnetic field. Such a shield could channel the particles from the coronal mass ejection to the poles, forming the aurora as on Earth and reducing the damage to the atmosphere.

However, orbiting so close to the star, Proxima Centauri b is likely to be in tidal lock as the moon is to the Earth. This is expected to weaken the magnetic field, as the slower rotation makes it harder to create a magnetic dynamo within the planet.

So if the protective shields are lowered on Proxima Centauri b, is our nearest planet a world populated by highly resistant UV organisms? Or have we seen evidence that rather than warming the planet to allow life to exist, this star has snuffed it out?

 

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Elizabeth Tasker
Elizabeth Tasker is an astrophysicist and science communicator at the Japan Aerospace Exploration Agency (JAXA). Her research explores the formation of stars and planets, while her science articles have covered topics from Egyptian coffins to deep sea drilling (but mainly focus on exoplanets and space missions!). While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

InSight Lands on Mars For Unique Mission

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NASA’s InSight Lander has returned its first picture from Mars via the MarCO CubeSat mission. (NASA)

 

NASA’s InSight lander touched down at 11:54 Pacific Time and followed a seven-month, 300 million-mile (485 million kilometer) journey from Southern California that started back in May.

InSight will spend the next few hours cleaning its camera lens and unfurling its solar arrays.

Once NASA confirms that the solar arrays have been properly deployed, engineers will spend the next three months preparing the lander’s science instruments to begin collecting data.

The touchdown continues NASA’s good fortunes with Mars landings, and is the fifth successful landing in a row.

Only 40% of missions by any agency sent to pass by, orbit or land on Mars have been successful, and NASA has certainly had some failures, too.

This is by way of saying that any successful mission to Mars is a great accomplishment.

The European Space Agency, the Indian Space Research Organisation and the team of ESA and Russia’s Roscosmos currently have satellites orbiting the planet, and Japan, China. Russia and the United Arab Emirates have Mars missions planned for the next decade.  The next NASA mission to the planet is the Mars 2020 rover, a follow-up to the still exploring Curiosity rover which landed in 2012.

 

For those who might have missed it, here is our recent Many Worlds column about the novel science planned for InSight:

 

An artist illustration of the InSight lander on Mars. InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is designed to look for tectonic activity and meteorite impacts, study how much heat is still flowing through the planet, and track Mars’ wobble as it orbits the sun. While InSight is a Mars mission, it will help answer key questions about the formation of the other rocky planets of the solar system and exoplanets beyond. (NASA/JPL-Caltech)

In the known history of our 4.5-billion-year-old solar system,  the insides of but one planet have been explored and studied.  While there’s a lot left to know about the crust, the mantle and the core of the Earth, there is a large and vibrant field dedicated to that learning.

Sometime next month, an extensive survey of the insides of a second solar system planet will begin.  That planet is Mars and, assuming safe arrival, the work will start after the InSight lander touches down on November 26.

This is not a mission that will produce dazzling images and headlines about the search for life on Mars.  But in terms of the hard science it is designed to perform, InSight has the potential to tell us an enormous amount about the makeup of Mars, how it formed, and possibly why is it but one-third the size of its terrestrial cousins, Earth and Venus.

“We know a lot about the surface of Mars, we know a lot about its atmosphere and even about its ionosphere,” says Bruce Banerdt, the mission’s principal investigator, in a NASA video. “But we don’t know very much about what goes on a mile below the surface, much less 2,000 miles below the surface.”

The goal of InSight is to fill that knowledge gap, helping NASA map out the deep structure of Mars.  And along the way, learn about the inferred formation and interiors of exoplanets, too.

Equitorial Mars and the InSight landing site, with noting of other sites. (NASA)

The lander will touch down at Elysium Planitia, a flat expanse due north of the Curiosity landing site.  The destination was selected because it is about as safe as a Mars landing site could be, and InSight did not need to be a more complex site with a compelling surface to explore.

“While I’m looking forward to those first images from the surface, I am even more eager to see the first data sets revealing what is happening deep below our landing pads.” Barerdt said. “The beauty of this mission is happening below the surface. Elysium Planitia is perfect.”

By studying the size, thickness, density and overall structure of the Martian core, mantle and crust, as well as the rate at which heat escapes from the planet’s interior, the InSight mission will provide glimpses into the evolutionary processes of all of the rocky planets in the inner solar system.

That’s because in terms of fundamental processes that shape planetary formation, Mars is an ideal subject.

It is big enough to have undergone the earliest internal heating and differentiation (separation of the crust, mantle and core) processes that shaped the terrestrial planets (Earth, Venus, Mercury, our moon), but small enough to have retained the signature of those processes over the next four billion years.

So Mars may contain the most in-depth and accurate record in the solar system of these processes. And because Mars has been less geologically active than the Earth — it does not have plate tectonics, for example —  it has retains a more complete evolutionary record in its own basic planetary building blocks.  In terms of deep planet geophysics,  it is often described as something of a fossil.

 

An artist rendering of the insides of rocky body like Mars.  The manner in which the different layers form and differentiate is seen as a central factor in whether the planet can become habitable.  (NASA)

 

By using geophysical instruments like those used on Earth, InSight will measure the fingerprints of the processes of terrestrial planet formation, as well as measuring the planet’s “vital signs.” They include the  “pulse” (seismology), “temperature” (heat flow probe), and “reflexes” (precision tracking).

One promising way InSight will peer into the Martian interior is by studying motion underground — what we know as marsquakes.

NASA has not attempted to do this kind of science since the Viking mission. Both Viking landers had their seismometers on top of the spacecraft, where they produced noisy data. InSight’s seismometer will be placed directly on the Martian surface, which will provide much cleaner data.

As described by the agency, “NASA have seen a lot of evidence suggesting Mars has quakes. But unlike quakes on Earth, which are mostly caused by tectonic plates moving around, marsquakes would be caused by other types of tectonic activity, such as volcanism and cracks forming in the planet’s crust.

“In addition, meteor impacts can create seismic waves, which InSight will try to detect.

“Each marsquake would be like a flashbulb that illuminates the structure of the planet’s interior. By studying how seismic waves pass through the different layers of the planet (the crust, mantle and core), scientists can deduce the depths of these layers and what they’re made of. In this way, seismology is like taking an X-ray of the interior of Mars.”

 

The InSight seismometer, developed by European partners and JPL, consists of a total of six seismic sensors that record the vibrations of the Martian soil in three directions in space and at two different frequency ranges. ges allows them to be mathematically combined into a single extremely broadband seismometer.  In order to protect the seismometer against wind and strong temperature fluctuations, a protective dome (Wind and Thermal Shield, WTS) will be placed over it. (German Aerospace Center)

 

Scientists think it’s likely they’ll see between a dozen and a hundred marsquakes over the course of two Earth years. The quakes are likely to be no bigger than a 6.0 on the Richter scale, which would be plenty of energy for revealing secrets about the planet’s interior.

Another area of scientific interest involves whether or not the core of Mars is liquid. InSight’s Rotation and Interior Structure Experiment, RISE, will help answer that question by tracking the location of the lander to determine just how much Mars’ North Pole wobbles as it orbits the sun.

These observations will provide information on the size of Mars’ iron-rich core and will help determine whether the core is liquid.  It will also help determine which other elements, besides iron, may be present.

The InSight science effort includes a self-hammering heat probe that will burrow down to 16 feet into the Martian soil and will for the first time measure the heat flow from the planet’s interior. Combining the rate of heat flow with other InSight data will reveal how energy within the planet drives changes on the surface.

This is especially important in trying to understand the presence and size of some of the solar system’s largest shield volcanoes in the solar system, a region known as Tharsis Mons.  Heat escaping from deep within the planet drives the formation of these types of features, as well as many others on rocky planets.

 

The Tharsis region of Mars has some of the largest volcanoes in the solar system. They include Olympus Mons, which is 375 miles in diameter and as much as 16 miles high. (U.S. Geological Survey)

InSight is not an astrobiology mission — no searching for life beyond Earth.

But it definitely is part of the process by which scientists will learn what planet formation and the dynamics of their interiors says about whether a planet can be home to life.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Barnard’s Star, The “Great White Whale” of Planet Hunting, Has Surrendered Its Secret

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Barnard’s Star is the closest single star to our sun, and the most fast moving. It has long been attractive to planet hunters because it is so close and so bright, especially in the infared section of the spectrum. But until now, the exoplanets of this “great white whale” have avoided detection.

 

Astronomers have found that Barnard’s star — a very close, fast-moving, and long studied red dwarf — has a super-Earth sized planet orbiting just beyond its habitable zone.

The discovery relied on data collected over many years using the tried-and-true radial velocity method, which searches for wobbles in the movement of the host star.

But this detection was something big for radial velocity astronomers because Barnard-b was among the smallest planet ever found using the technique, and it was the furthest out from its host star as well — orbiting its star every 233 days.

For more than a century, astronomers have studied Barnard’s star as the most likely place to find an extrasolar planet.

Ultimately, said Ignasi Rablis of Spain’s Institute of Space Studies of Catalonia, lead author of the paper in journal Nature, the discovery was the result of 771 observations, an extremely high number.

And now, he said, “after a very careful analysis, we are over 99 percent confident the planet is there.”

The planet is at least 3.2 times the size of Earth and orbits near the snowline of the system, where water cannot be expected to ever be liquid.  That means is it a frozen world (an estimated -150 degrees Celsius) and highly unlikely to support life.

But Rablis and others on the large team say it also an extremely good candidate for future direct imaging and next-generation observing.

 

An artist’s rendering of the Barnard’s star planet at sunset. (Martin Kornmesser/ESO)

 

Thousands of exoplanets have been identified by now, and hundreds using the radial velocity method.  But this one is different.

“Barnard’s star is the ‘great white whale’ of planet hunting,” said Paul Butler, senior scientist at the Carnegie Institution, a radial velocity pioneer, and one of the numerous authors of the paper.

Because the star is so close (but 6 light-years away) and as a result so tempting, it has been the subject of exoplanet searches for 100 years, Butler said.  But until the radial velocity breakthroughs of the mid 1990s, the techniques used could not find a planet.

Nonetheless, an early exoplanet hunter, the Dutch-American astronomer Peter van de Kamp of Swarthmore College, thought that he had indeed found two gas giant planets around Barnard’s star in the 1960s.  He used a different technique based on the movement of the host star, and the findings even made it into some textbooks.  But later the detection was found to be incorrect.

Even after the modern exoplanet era began Barnard’s star kept its planetary secret close.

As Butler explained it, the combination of the planet’s size and distance from the star ultimately pushed the technology (and astronomers) to the very limit — requiring a measurement of  1.2 meters per second of “wobble.”

In contrast, the first planets were found by radial velocity that would detect 70 meter per second of wobble caused by the gravitational pull of a planet, and 30 years ago the best instruments could detect only 300 meters per second.

 

The radial velocity technique identifies planets via the shift in the wavelength of the light of a star as it wobbles due to the presence of a planet.  When a celestial object moves away from us, the light we observe becomes slightly less energetic and redder.  The opposite — light becomes slightly more energetic and bluer — happens when the star moves toward us.

 

The detected planet (which remains a “candidate” until further confirmed) was ultimately found following concerted effort by a large team of astronomers around the world.  It was co-led and organized by Guillem Anglada-Escudé of the Queen Mary University of London.  The young astronomer had made a major splash in 2016 with the detection of a planet orbiting Proxima Centauri, the closest star to our own.

That discovery was part of the “Pale Red Dot” campaign, which had the goal of detecting rocky planets around red dwarf stars.  After the Proxima discovery Barnard’s star went to the top of Anglada-Escudé list with the renamed “Red Dots” collaboration — which is supported by the European Southern Observatory and universities in Chile, the United Kingdom, Spain and Germany.

The Red Dots campaign is a collaboration including the European Southern Observatory, Queen Mary University of London, and several European and South American institutions.

By 2015, there was already almost 18 years of modern data collected regarding a possible planet orbiting the star, and a faint but clearly present signal had been detected.  But more was needed to confidently report a discovery, and the Red Dots effort took up the challenge.

To see if the result could be confirmed, astronomers regularly monitored Barnard’s star with high precision spectrometers such as the CARMENES (Calar Alto Observatory in Spain), and also the HARPS  (High Accuracy Radial velocity Planet Searcher.)

Ultimately, the team used observations from seven different instruments taken over 20 years, making this one of the largest and most extensive datasets ever used for precise radial velocity studies.

“We all have worked very hard on this result,” said Anglada-Escudé. “This is the result of a large collaboration organized in the context of the Red Dots project, which is why it has contributions from teams all over the world including semi-professional astronomers.”

Cristina Rodríguez-López, researcher at the Instituto de Astrofísica de Andalucía and co-author of the paper, said of the significance of the finding grow over decades.

Guillem Anglada-Escudé was a leader of the Barnard’s star collaboration, as he was in the successful campaign to detect a planet orbiting of Proxima Centauri.

“This discovery means a boost to continue on searching for exoplanets around our closest stellar neighbors, in the hope that eventually we will come upon one that has the right conditions to host life,” she said.

The next pr0ject for the Red Dots campaign is to study the star Ross 154, at 9.69 light-years away another of the closest stars to us.

The dramatically increased (and increasing) precision in radial velocity measurements is expected to continue with the next generation of ground-based telescopes and spectrometers.

Butler, for instance,  said that Carnegie is in the process of upgrading its Planet Finding Spectrograph at the Las Campanas Observatory in Chile to reach a 0.5-meters-per-second measurement. Other groups including the European Southern Observatory and American teams based at Pennsylvania State and Yale Universities have similar efforts under way.

If they succeed, Butler said, it may well be possible to find potentially habitable planets around sun-like and other categories of stars using the radial velocity method.

 

 

Barnard’s star is the fourth closest to our sun, and the closest single star. It lies 6 light-years from us, as opposed to a little more than 4 light-years for the Alpha Centauri/Proxima Centauri threesome. (NASA Photojournal)

 

Barnard’s a very-low-mass red dwarf star in the constellation of Ophiuchus. It is the fourth-nearest-known individual star to the sun (after the three components of the Alpha Centauri system) and the closest star in the Northern Celestial hemisphere.

Despite its proximity, the star is too faint to be seen with the unaided eye, though it is quite visible with an amateur 8-inch telescope.  It is much brighter in the infrared than in visible light.  Although Barnard’s Star is an ancient star, it still experiences star flare events, one being observed in 1998.

The star is named after the American astronomer E. E. Barnard.  He was not the first to observe the star (it appeared on Harvard University plates in 1888 and 1890), but in 1916 he measured its proper motion –the apparent angular motion of a star across the sky with respect to more distant stars — as 10.3 arcseconds per year relative to the sun.

This is likely to be the fastest star in terms of proper motion, as its proximity to the sun, as well as its high velocity, make it unlikely any faster object will be discovered.

Barnard’s Star is among the most studied red dwarfs because of its proximity and favorable location for observation near the celestial equator. Historically, research on Barnard’s Star has focused on measuring its stellar characteristics and its astrometry — which involves precise measurements of the positions and movements of stars and other celestial bodies on the plane of the sky.

When planet hunters use astrometry, they look for a minute but regular wobble in a star’s position as seen in images.  Van de Kamp, for instance, used astrometry to study Barnard’s star and (incorrectly) detected those two gas giants around it.

In contrast, radial (or Doppler) velocities look for the wobble of the star perpendicular to the plane sky, and astronomers have regularly, and now once again, made history with that method.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Probing The Insides of Mars to Learn How Rocky Planets Are Formed

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An artist illustration of the InSight lander on Mars. InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is designed to look for tectonic activity and meteorite impacts, study how much heat is still flowing through the planet, and track Mars’ wobble as it orbits the sun. While InSight is a Mars mission, it will help answer key questions about the formation of the other rocky planets of the solar system and exoplanets beyond. (NASA/JPL-Caltech)

In the known history of our 4.5-billion-year-old solar system,  the insides of but one planet have been explored and studied.  While there’s a lot left to know about the crust, the mantle and the core of the Earth, there is a large and vibrant field dedicated to that learning.

Sometime next month, an extensive survey of the insides of a second solar system planet will begin.  That planet is Mars and, assuming safe arrival, the work will start after the InSight lander touches down on November 26.

This is not a mission that will produce dazzling images and headlines about the search for life on Mars.  But in terms of the hard science it is designed to perform, InSight has the potential to tell us an enormous amount about the makeup of Mars, how it formed, and possibly why is it but one-third the size of its terrestrial cousins, Earth and Venus.

“We know a lot about the surface of Mars, we know a lot about its atmosphere and even about its ionosphere,” says Bruce Banerdt, the mission’s principal investigator, in a NASA video. “But we don’t know very much about what goes on a mile below the surface, much less 2,000 miles below the surface.”

The goal of InSight is to fill that knowledge gap, helping NASA map out the deep structure of Mars.  And along the way, learn about the inferred formation and interiors of exoplanets, too.

Equitorial Mars and the InSight landing site, with noting of other sites. (NASA)

The lander will touch down at Elysium Planitia, a flat expanse due north of the Curiosity landing site.  The destination was selected because it is about as safe as a Mars landing site could be, and InSight did not need to be a more complex site with a compelling surface to explore.

“While I’m looking forward to those first images from the surface, I am even more eager to see the first data sets revealing what is happening deep below our landing pads.” Barerdt said. “The beauty of this mission is happening below the surface. Elysium Planitia is perfect.”

By studying the size, thickness, density and overall structure of the Martian core, mantle and crust, as well as the rate at which heat escapes from the planet’s interior, the InSight mission will provide glimpses into the evolutionary processes of all of the rocky planets in the inner solar system.

That’s because in terms of fundamental processes that shape planetary formation, Mars is an ideal subject.

It is big enough to have undergone the earliest internal heating and differentiation (separation of the crust, mantle and core) processes that shaped the terrestrial planets (Earth, Venus, Mercury, our moon), but small enough to have retained the signature of those processes over the next four billion years.

So Mars may contain the most in-depth and accurate record in the solar system of these processes. And because Mars has been less geologically active than the Earth — it does not have plate tectonics, for example —  it has retains a more complete evolutionary record in its own basic planetary building blocks.  In terms of deep planet geophysics,  it is often described as something of a fossil.

 

An artist rendering of the insides of rocky body like Mars.  The manner in which the different layers form and differentiate is seen as a central factor in whether the planet can become habitable.  (NASA)

 

By using geophysical instruments like those used on Earth, InSight will measure the fingerprints of the processes of terrestrial planet formation, as well as measuring the planet’s “vital signs.” They include the  “pulse” (seismology), “temperature” (heat flow probe), and “reflexes” (precision tracking).

One promising way InSight will peer into the Martian interior is by studying motion underground — what we know as marsquakes.

NASA has not attempted to do this kind of science since the Viking mission. Both Viking landers had their seismometers on top of the spacecraft, where they produced noisy data. InSight’s seismometer will be placed directly on the Martian surface, which will provide much cleaner data.

As described by the agency, “NASA have seen a lot of evidence suggesting Mars has quakes. But unlike quakes on Earth, which are mostly caused by tectonic plates moving around, marsquakes would be caused by other types of tectonic activity, such as volcanism and cracks forming in the planet’s crust.

“In addition, meteor impacts can create seismic waves, which InSight will try to detect.

“Each marsquake would be like a flashbulb that illuminates the structure of the planet’s interior. By studying how seismic waves pass through the different layers of the planet (the crust, mantle and core), scientists can deduce the depths of these layers and what they’re made of. In this way, seismology is like taking an X-ray of the interior of Mars.”

 

The InSight seismometer, developed by European partners and JPL, consists of a total of six seismic sensors that record the vibrations of the Martian soil in three directions in space and at two different frequency ranges. ges allows them to be mathematically combined into a single extremely broadband seismometer.  In order to protect the seismometer against wind and strong temperature fluctuations, a protective dome (Wind and Thermal Shield, WTS) will be placed over it. (German Aerospace Center)

 

Scientists think it’s likely they’ll see between a dozen and a hundred marsquakes over the course of two Earth years. The quakes are likely to be no bigger than a 6.0 on the Richter scale, which would be plenty of energy for revealing secrets about the planet’s interior.

Another area of scientific interest involves whether or not the core of Mars is liquid. InSight’s Rotation and Interior Structure Experiment, RISE, will help answer that question by tracking the location of the lander to determine just how much Mars’ North Pole wobbles as it orbits the sun.

These observations will provide information on the size of Mars’ iron-rich core and will help determine whether the core is liquid.  It will also help determine which other elements, besides iron, may be present.

The InSight science effort includes a self-hammering heat probe that will burrow down to 16 feet into the Martian soil and will for the first time measure the heat flow from the planet’s interior. Combining the rate of heat flow with other InSight data will reveal how energy within the planet drives changes on the surface.

This is especially important in trying to understand the presence and size of some of the solar system’s largest shield volcanoes in the solar system, a region known as Tharsis Mons.  Heat escaping from deep within the planet drives the formation of these types of features, as well as many others on rocky planets.

 

The Tharsis region of Mars has some of the largest volcanoes in the solar system. They include Olympus Mons, which is 375 miles in diameter and as much as 16 miles high. (U.S. Geological Survey)

InSight is not an astrobiology mission — no searching for life beyond Earth.

But it definitely is part of the process by which scientists will learn what planet formation and the dynamics of their interiors says about whether a planet can be home to life.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

The Kepler Space Telescope Mission Is Ending But Its Legacy Will Keep Growing.

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An illustration of the Kepler Space Telescope, which is on its very last legs.  As of October 2018, the planet-hunting spacecraft has been in space for nearly a decade. (NASA via AP)

 

The Kepler Space Telescope is dead.  Long live the Kepler.

NASA officials announced on Tuesday that the pioneering exoplanet survey telescope — which had led to the identification of almost 2,700 exoplanets — had finally reached its end, having essentially run out of fuel.  This is after nine years of observing, after a malfunctioning steering system required a complex fix and change of plants, and after the hydrazine fuel levels reached empty.

While the sheer number of exoplanets discovered is impressive the telescope did substantially more:  it proved once and for all that the galaxy is filled with planets orbiting distant stars.  Before Kepler this was speculated, but now it is firmly established thanks to the Kepler run.

It also provided data for thousands of papers exploring the logic and characteristics of exoplanets.  And that’s why the Kepler will indeed live long in the world of space science.

“As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington.

“Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”

 

 


The Kepler Space Telescope was focused on hunting for planets in this patch of the Milky Way. After two of its four spinning reaction wheels failed, it could no longer remain steady enough to stare that those distant stars but was reconfigured to look elsewhere and at a different angle for the K2 mission. (Carter Roberts/NASA)

 

Kepler was initially the unlikely brainchild of William Borucki, its founding principal investigator who is now retired from NASA’s Ames Research Center in California’s Silicon Valley.

When he began thinking of designing and proposing a space telescope that could potentially tell us how common distant exoplanets were — and especially smaller terrestrial exoplanets like Earth – the science of extra solar planets was at a very different stage.

William Borucki, originally the main champion for the Kepler idea and later the principal investigator of the mission. His work at NASA went back to the Apollo days. (NASA)

“When we started conceiving this mission 35 years ago we didn’t know of a single planet outside our solar system,” Borucki said.  “Now that we know planets are everywhere, Kepler has set us on a new course that’s full of promise for future generations to explore our galaxy.”

The space telescope was launched in 2009.  While Kepler did not find the first exoplanets — that required the work of astronomers using a different technique of observing based on the “wobble” of stars caused by orbiting planets — it did change the exoplanet paradigm substantially.

Not only did it prove that exoplanets are common, it found that planets outnumber stars in our galaxy (which has hundreds of billions of those stars.)

In addition it found that small, terrestrial-size planets are common as well, with some 20 to 50 percent of stars likely to have planets of that size and type.  And what menagerie of planets it found out there.

Astrophysicist Natalie Batalha was the Kepler project and mission scientist for a decade. She left NASA recently for the University of California at Santa Cruz “to carry on the Kepler legacy” by creating an interdisciplinary center for the study of planetary habitability.

Among the greatest surprises:  The Kepler mission provided data showing that the most common sized planets in the galaxy fall somewhere between Earth and Neptune, a type of planet that isn’t present in our solar system.

It found solar systems of all sizes as well, including some with many planets (as many as eight) orbiting close to their host star.

The discovery of these compact systems, generally orbiting a red dwarf star, raised questions about how solar systems form: Are these planets “born” close to their parent star, or do they form farther out and migrate in?

So far, more than 2,500 peer-reviewed papers have been published using Kepler data, with substantial amounts of that data still unmined.

Natalie Batalha was the project and mission scientist for Kepler for much of its run, and I asked her about its legacy.

“When I think of Kepler’s influence across all of astrophysics, I’m amazed at what such a simple experiment accomplished,” she wrote in an email. “You’d be hard-pressed to come up with a more boring mandate — to unblinkingly measure the brightnesses of the same stars for years on end. No beautiful images. No fancy spectra. No landscapes. Just dots in a scatter plot.

“And yet time-domain astronomy exploded. We’d never looked at the Universe quite this way before. We saw lava worlds and water worlds and disintegrating planets and heart-beat stars and supernova shock waves and the spinning cores of stars and planets the age of the galaxy itself… all from those dots.”

 

The Kepler-62 system is put one of many solar systems detected by the space telescope. The planets within the green discs are in the habitable zones of the stars — where water could be liquid at times. (NASA)

 

While Kepler provided remarkable answers to questions about the overall planetary makeup of our galaxy, it did not identify smaller planets that will be directly imaged, the evolving gold standard for characterizing exoplanets.  The 150,000 stars that the telescope was observing were very distant, in the range of a few hundred to a few thousand light-years away. One light year is about 6 trillion (6,000,000,000,000) miles.

Nonetheless, Kepler was able to detect  the presence of a handful of Earth-sized planets in the habitable zones of their stars.  The Kepler-62 system held one of them, and it is 1200 light-years away.  In contrast, the four Earth-sized planets in the habitable zone of the much-studied Trappist-1 system are 39 light-years away.

Kepler made its observations using the the transit technique, which looks for tiny dips in the amount of light coming from a star caused by the presence of a planet passing in front of the star.  While the inference that exoplanets are ubiquitous came from Kepler results, the telescope was actually observing but a small bit of the sky.  It has been estimated that it would require around 400 space telescopes like Kepler to cover the whole sky.

What’s more, only planets whose orbits are seen edge-on from Earth can be detected via the transit method, and that rules out a vast number of exoplanets.

The bulk of the stars that were selected for close Kepler observation were more or less sun-like, but a sampling of other stars occurred as well. One of the most important factors was brightness. Detecting minuscule changes in brightness caused by transiting planet is impossible if the star is too dim.

 

The artist’s concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone. (NASA Ames/SETI Institute/JPL-Caltech)

 

Four years into the mission, after the primary mission objectives had been met, mechanical failures temporarily halted observations. The mission team was able to devise a fix, switching the spacecraft’s field of view roughly every three months. This enabled an extended mission for the spacecraft, dubbed K2, which lasted as long as the first mission and bumped Kepler’s count of surveyed stars up to more than 500,000.

But it was inevitable that the mission would come to an end sooner rather than later because of that dwindling fuel supply, needed to keep the telescope properly pointed.

Kepler cannot be refueled because NASA decided to place the telescope in an orbit around the sun that is well beyond the influence of the Earth and moon — to simplify operations and ensure an extremely quiet, stable environment for scientific observations.  So Kepler was beyond the reach of any refueling vessel.  The Kepler team compensated by flying considerably more fuel than was necessary to meet the mission objectives.

The video below explains what will happen to the Kepler capsule once it is decommissioned.  But a NASA release explains that the final commands “will be to turn off the spacecraft transmitters and disable the onboard fault protection that would turn them back on. While the spacecraft is a long way from Earth and requires enormous antennas to communicate with it, it is good practice to turn off transmitters when they are no longer being used, and not pollute the airwaves with potential interference.”

 

 

And so Kepler will actually continue orbiting for many decades, just as its legacy will continue long after operations cease.

Kepler’s follow-on exoplanet surveyor — the Transiting Exoplanet Survey Satellite or TESS — was launched this year and has begun sending back data.  Its primary mission objective is to survey the brightest stars near the Earth for transiting exoplanets. The TESS satellite uses an array of wide-field cameras to survey some 85% of the sky, and is planned to last for two years.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.