Category: The Search for Life Beyond Earth (page 2 of 9)

Can We Trust a Handful of Grains to Tell Us About the Early Earth? A Look at the Hayabusa2 Asteroid Sample

The Hayabusa2 sample return capsule returning to Earth. The bright streak in the sky is the capsule, shock heated as it enters the Earth’s atmosphere. The bright lights on the ground are buildings. (JAXA)

In the early hours of December 6, 2020, what appeared to be a shooting star blazed across the sky above the Woomera desert in South Australia. The source was the sample return capsule from JAXA’s Hayabusa2 mission, which contained precious material from a near-Earth asteroid known as Ryugu.

Within 60 hours, the capsule had been retrieved and flown to the curation facility at JAXA’s Institute of Space and Astronautical Science in Japan. In vacuum conditions to prevent any trace of contamination, the capsule was opened to reveal over 5 grams of asteroid grains.

This material is expected to have undergone little change since the early days of the solar system some 4.5 billion years ago, and its highly anticipated analysis could provide new information about how the Earth acquired water and organics needed to begin life. The sample is the first ever collected from a carbonaceous (C-type) asteroid, which resemble primitive meteorites found to have a chemical composition close to that of the Sun.

Tet despite a rigorously planned and executed journey of over 5,000 million kilometers to bring back a pristine sample from space, concerns have remained. Chief among these are whether the rocky grains in the sample capsule were typical of the asteroid.

If the Hayabusa2 spacecraft had inadvertently gathered grains from an unusual spot, or if the grains had been altered during the collection and return to Earth, then deductions about the asteroid’s composition–and therefore our solar system’s past–could be wrong.  

The sample from asteroid Ryugu (from Yada et al. Nature Astronomy 2021)

The Hayabusa2 team had already gone to rather extreme lengths to mitigate this issue.

In addition to the rapid retrieval operation that ensured that the sample was not contaminated by our planet’s atmosphere, the spacecraft had performed the dangerous landing twice on the surface of asteroid Ryugu to collect samples from two separate sites.

One of these locations was close to where the spacecraft had made an artificial crater, ejecting material from beneath the asteroid’s surface to be gathered during the second collection operation. Rocky grains from below the top layer surface are expected to be particularly pristine, as they have been protected from the bombardment of sunlight, cosmic rays and micrometeorites.… Read more

More On The Very Hot Science of Stellar Flares and Their Implications For Habitability

A solar flare, imaged by NASA’s Solar Dynamics Observatory.

Among the many scientific fields born, or reborn, by the rise of astrobiology and its search for life beyond Earth is the study of stars, including our own Sun.  Now that we know that planets — from the large and gaseous to the small and rocky — are common in our galaxy and number in the many, many billions, there is suddenly vast amount of real estate where life potentially could arise.

We already know that many of those planets large and small are not candidates for habitability for any number of reasons, and that makes the understanding of what general conditions are required for life all the more pressing.

And as the astrobiological effort speeds ahead, it has become clear that the make-up, behavior and location of the stars that host exoplanets is central to that understanding.

Many stellar issues are suddenly important, and perhaps none more so than the nature, frequency and consequences of the constant stellar eruption of  flares, superflares and coronal mass ejections.

Created as intense bursts of radiation coming from the release of magnetic energy following reconnections in stars’ coronas, flares and related coronal mass ejections are the largest explosive events in solar systems. The energy released by a major flare from our Sun is about a sixth of the total solar energy released each second and equal to 160,000,000,000 megatons of TNT

The current focus of study is flares coming off red dwarf stars — much smaller and less energetic than our Sun, but the most common stars in the galaxy, by a lot.  Many are already known to have multiple rocky planets within a distance from the star termed the “habitable zone,” where in theory water could sometimes be liquid.

But red dwarf stars universally experience intense flaring in their early periods, and the planets orbiting in the those red dwarf habitable zones can be 20 times closer to their stars than we are to the Sun.

The crucial question is whether those flares forever sterilize the planets in their systems, which is certainly a possibility.  But a related question is whether the flares might also deliver amounts of ultraviolet radiation that may be essential to the formation of the chemical building blocks of life.

Not surprisingly, this is a subject of not only intense study but of heated debate as well.

Violent stellar flares from young red dwarf stars, as illustrated here, could potentially evaporate the atmosphere of a planet.

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“Tantalizing” Carbon Signals From Mars

This mosaic was made from images taken by the Mast Camera aboard NASA’s Curiosity rover on the 2,729th Martian day, or sol, of the mission. It shows the landscape of the Stimson sandstone formation in Gale crater. In this general location, Curiosity drilled the Edinburgh hole, a sample from which was enriched in carbon-12. (NASA/JPL-Caltech/MSSS.)

The rugged and parched expanses of Western Australia are where many of the oldest signs of ancient life on Earth have been found, embedded in the sedimentary rocks that have been undisturbed there for eons.  One particularly significant finding from the Tumbiana Formation contained a substantial and telltale excess of the carbon-12 isotope compared with carbon-13.

Since carbon 12 is used by living organisms, that carbon-12 excess in the rocks was interpreted to mean that some life-form had been present long ago (about 2.7 billion years) and left behind that “signature”  of its presence. What was once a microbial mat that could have produced the carbon-12 excess was ultimately found nearby.

After nine years of exploring Gale Crater on Mars, scientists with NASA’s Curiosity rover have collected a substantial number of rock samples that they have similarly drilled, pulverized, gasified and analyzed.

And as explained in an article in the Proceedings of the National Academy of Science (PNAS,) researchers have found quite a few Martian specimen that have the same carbon-12 excesses as those found in Western Australia.

Paul Mahaffy of NASA’s Goddard Space Flight Center, long-time principal investigator for the instrument that found the carbon-12 excess on Mars, called the results “tantalizingly interesting.”

And the lead author of the PNAS paper, Christopher House of Penn State University, said that “On Earth, processes that would produce the carbon signal we’re detecting on Mars are biological.”  Like from Western Australia and elsewhere.

So something unusual and important has been discovered. But exactly what it is and how it came to be remains very much a work in progress.

Perhaps biology did play a role, the team writes.  If so, it would involve ancient bacteria in the Martian surface that would have produced a unique carbon signature when they released methane into the atmosphere. Ultraviolet light would have then converted that gas into larger, more complex molecules that would rain down and become part of Martian rocks.

Scientists with NASA and European Mars missions traveled to the Western Australian Outback to hone their research techniques before their missions launched.

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A Huge Watery Reservoir May Lie Beneath the Surface of The “Grand Canyon” of Mars

The Valles Marineris in equatorial Mars and is one of the the largest canyon in the solar system.  It is surpassed in length only by the rift valleys of Earth. (NASA)

That early Mars was much wetter and warmer than it is today has been well established by numerous missions.  Water ice is visible at the poles and many fossil rivers have been found in the southern highlands of Mars.  The Curiosity rover found as well that the large crater where it landed — Gale Crater – once had a lake and in-flowing streams.

But the presence of water, or proof that water once flowed, has been missing in the equatorial latitudes  of the planet.

However, now a paper based on data from the European/Russian Trace Gas Orbiter (TGO) strongly suggests that the Candor Chasma, located near the heart of the massive canyon system called Valles Marineris, has either large deposits of a kind of permafrost water ice just below its surface or of rocks formed in water and now containing that H2O in their structure.

The article to appear in the journal Icarus says that the discovery of large amounts of hydrogen in the region speaks of this aqueous  past.

“We found a central part of Valles Marineris to be packed full of water – far more water than we expected,” Alexey Malakhov, of the Russian Space Research Institute and a co-author of the study, said in a statement.

“This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures.”

 

Valles Marineris, seen at an angle of 45 degrees to the surface in near-true color and with four times vertical exaggeration. The image covers an area of about 400,000 square miles. The largest portion of the canyon, which spans right across the image, is known as Melas Chasma. Candor Chasma is the connecting trough immediately to the north. The digital terrain model was created from 20 images taken by the High Resolution Stereo Camera of the Mars Express Orbiter. (ESA)

Valles Marineris is 10 times longer and 4 times deeper than our Grand Canyon.  Geologists have theorized that Valles Marineris began to open along geological faults about 3.5 billion years ago. The faulting may have been caused by the tectonic activity that accompanied the growth of the giant volcanoes in Tharsis, lying just to the west.Read more

What The James Webb Space Telescope Can Do For Exoplanet Science and What It Cannot Do

The James Webb Space Telescope, as rendered by an artist. The telescope is scheduled to launch later this month. (NASA)

When the James Webb Space Telescope finally launches (late this month, if the schedule holds) it will forever change astronomy.

Assuming that its complex, month-long deployment in space works as planned, it will become the most powerful and far-seeing observatory in the sky.  It will have unprecedented capabilities to probe the earliest days of the universe, shedding new light on the formation of the first stars and galaxies.  And it will observe in new detail the most distant regions of our solar system.

Deep space astrophysics is what JWST was first designed for in the early 1990s, and that will be its transformative strength.

But much is also being made of what JWST can do for the study of exoplanets and some are even talking about how it just might be able to find biosignatures — signs of distant life.

While it is probably wise to never say never regarding an observatory with the power and capabilities of JWST,  the reality is that it was not designed to look for the exoplanets most likely to be habitable.  Actually, when it was first proposed, the observatory had no exoplanet-studying capabilities at all because no exoplanets had yet been found.

What was added on is substantial and exoplanet scientists say JWST can help advance the field substantially.  But there are definite limits and finding biosignatures — life — is almost certainly a reach too far for JWST.

When starlight passes through a planet’s atmosphere, certain parts of the light are absorbed by the atmosphere’s elements. By studying which parts of light are absorbed, scientists can determine the composition of the planet’s atmosphere. (Christine Daniloff/MIT, Julien de Wit)

Astronomer Jacob Bean of the University of Chicago, who has played a leadership role in planning JWST exoplanet observations for the telescope’s early day, says that people need to know these limitations so the pioneering exoplanet science that will be possible with JWST is not seen as somehow disappointing.

As he explained, it is essential to understand that the kind of exoplanet observing that the JWST will mostly do is “transit spectroscopy.”  This involves staring at a star when an exoplanet is expected to transit in front of it.  When that happens, light from the star will pass through the atmosphere of the exoplanet (if there is one) and through spectroscopy scientists can determine what molecules are in that hoped-for atmosphere.… Read more

NASA Should Build a Grand Observatory Designed to Search For Life Beyond Earth, Top Panel Concludes

The National Academy of Sciences has released it’s “Decadal Survey,” with guidance and recommendations for the fields of astronomy, astrobiology and astrophysics.(NASA)

NASA should begin developing a mission that can tell us whether life in the near galaxy is abundant, rare or essentially absent, The National Academy of Sciences recommended yesterday.

The call for a next Grand Observatory telescope with this ambitious goal represents the first time that the Academy, in its Decadal Survey for Astronomy and Astrophysics, has given top priority to the science of  exoplanets and the search for life far beyond Earth.

The long-awaited NAS survey did not select a single mission concept, although several NASA-commissioned studies were extensively researched and assembled for the Decadal over the past four years.

Rather, they set the science goal of giving an answer – as complete as possible – to the eternally-asked question of whether life exists solely on Earth or can be found on the billions of other planets we now know orbit their own suns.

Decadal steering committee co-chair Robert Kennicutt Jr., a professor at University of Arizona and Texas A & M University, said that a flood of discoveries and astronomical and technological advances in recent decades made clear that the time for such a mission had come.

“We’re laying down a marker here,” Kennicutt said  in a press conference.  “We think that progress in this field has taken us to the point that within the planning horizon of this survey, we can really contemplate imaging  Earth-like planets in their habitable zones around other stars and spectroscopically studying them for atmospheric composition, perhaps including biomarkers. with the ultimate goal of answering one of the most profound questions:  Are we alone in the universe?”

The proposed mission, he said, would as a result have the transformative scientific power of the Hubble Space Telescope and the James Webb Space Telescope, which is scheduled to launch next month.  It would change the way that scientists and citizens see the world.

The telescope envisioned by Decadal Survey would search for small rocky planets in the habitable zone of heir sun — where the temperatures would allow for liquid water to exist rather than just water vapor or ice.  This artist’s concept ia of Kepler-452b, the first near-Earth-size world found in the habitable zone of a distant sun-like star. ( NASA/Ames/JPL-Caltech.)

But the road to an actual mission will be long and definitely uphill.… Read more

Many Planets Form in a Soup of Life-Friendly Organic Compounds

Artist’s depiction of a protoplanetary disk with young planets forming around a star. The right-side panel zooms in to show various organic molecules that are accreting onto a planet. (M.Weiss/Center for Astrophysics | Harvard & Smithsonian)

One of the more persuasive arguments in favor of the potential existence of life beyond Earth is that the well-known chemical building blocks of that life are found throughout the galaxy.  These chemical components aren’t all present in all examined solar systems and planets, but they are common and behave in ways familiar to scientists here.

And when it comes elements and compounds found on distant planets but not found here, there just aren’t many. That doesn’t mean they don’t exist — some unstable compounds in interstellar space, for instance — but rather that the cosmos holds many surprises but none have involved extraterrestrial elements or compounds near planets or stars.

This is in large part the result of how elements are formed in the universe.  Other than hydrogen and helium, all other elements are forged in the thermonuclear explosion of stars that have exhausted their supply of fuel.  These massive explosions (supernovae) then shoot the newly-formed elements out into space where they can and do collect in gas and dust clouds that will form other new stars.  They are spread throughout the disks that form around new stars and over time they become components of new planets in formation.

This galactic evolution includes the bonding together of carbon-based organic compounds — the building blocks of life as we know it.  They are an essential component to any theory of a planet’s habitability and,  while their presence in space and star nurseries has been known for some time,  they have remained a subject of great interest but limited detailed knowledge.

That is why an international team from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. set out to intensively study five disks forming around young stars to determine more precisely what organic compounds were present and available for objects developing into planets.

And the results are striking:  The abundance of organic material detected was 10 to 100 times more than expected.

“These planet-forming disks are teeming with organic molecules, some of which are implicated in the origins of life here on Earth,” said team leader Karin Öberg. “This is really exciting; the chemicals in each disk will ultimately affect the type of planets that form and determine whether or not the planets can host life.”… Read more

Frigid Europa Holds a Huge and Maybe Habitable Ocean Beneath Its Thick Ice Covering. How is That Possible?

Europa has one of the smoothest surface of any body in the solar system.  A moon as old as Europa that did not have an ice cover — and a likely ocean inside — would be pocked with asteroid craters.  On Europa, these craters appear to be absorbed into the icy surface via geologic and thermal processes.  Giant lakes trapped in Europa’s crust also bust up the icy surface. (NASA)

Jupiter’s moon Europa is almost five times as far away from the sun as Earth is, with surface temperatures that don’t rise above minus 260 degrees Fahrenheit.  It’s slightly smaller than our moon and orbits but 400,000 miles from the solar system’s largest planet, which it takes but 3.5 Earth days to orbit.  As a result it is tidally locked, always showing the same face to Jupiter.

When it comes to potentially habitable objects in our solar system, Europa would not seem to be a terribly likely possibility.

But, of course, it is.  And in three years NASA’s Europa Clipper mission will launch to explore what would appear to be one of the most unlikely yet possible places in our solar system to find potential signs of life.

The reason why is that scientists are almost certain that under Europa ‘s 10-to 15 mile ice covering is a deep, global ocean of salty water.

The size of the ocean has not been well determined yet, with estimates of between 40 and 100 miles of depth.  But a  consensus has been reached that the ocean is likely to be global, and contains two to three times as much liquid water as found on Earth.

This then raises a question with great significance for Europa, other moons in the solar system and quite likely planets and moons well beyond us:  How can there be so much liquid water inside such frigid places?

The spot toward the lower left is one Europa, against the backdrop of Jupiter.  Images from Voyager in 1979 bolster the modern hypothesis that Europa has an underground ocean and is therefore a good place to look for extraterrestrial life. The dark spot on the upper right is a shadow of another of Jupiter’s large moons. Sixteen frames from Voyager 1’s 1979 Jupiter flyby were recently reprocessed and merged to create this image.  (NASA, Voyager 1, JPL, Caltech; Processing & License: Alexis Tranchandon / Solaris)

There are numerous possible answers to that question, and it’s likely that all or most played some role.… Read more

Sample Return from Mars Begins in Earnest

This image taken by NASA’s Perseverance rover on Sept. 7, 2021 shows two holes where the rover’s drill obtained chalk-size samples from a rock nicknamed “Rochette.” They are the first physical manifestations of the NASA’s long-planned Mars Sample Return Mission. (NASA/JPL-Caltech.)

For the first time ever, a sample of pulverized rock from another planet has been drilled, collected and stored for eventual delivery to the highest-tech labs on Earth.

Yes, a storehouse of rocks were collected on the moon by Apollo astronauts and delivered to Houston, and some small samples of two asteroids and one comet were snatched by three spacecraft (two Japanese and one American) and their contents were brought here for study.

But never before has the surface of another planet been the source of precious extraterrestrial material that some day, if all goes well, will be received on Earth for intensive analysis.

The feat was accomplished by the team that operates the Perseverance rover on Mars.  After an unsuccessful effort to drill what turned out to be a very soft rock in August , the rover drill succeeded in digging into a briefcase-sized hard volcanic rock twice this month and pulling out samples to be tubed and stored for later pick-up by a different mission.

That next step isn’t scheduled for another half decade and the samples would not arrived on Earth until well after that.  But a long-dreamed and highly-ambitious effort to bring some of Mars to Earth (called Mars Sample Return) has now formally begun.

“This is a truly historic achievement, the very first rock cores collected on another terrestrial planet — it’s amazing,” Meenakshi Wadhwa, Mars sample return principal scientist at NASA’s Jet Propulsion Laboratory, said during a news conference held Friday

“In our science community, we’ve talked about Mars sample return for decades,” Wadhwa said. “And now it’s actually starting to feel real.”

Perseverance’s first cored-rock sample of Mars is seen inside its titanium container tube in this image taken by the rover’s Sampling and Caching System Camera, known as CacheCam. (NASA/JPL-Caltech)

The press conference was a victory lap of sorts for leaders of a team with many members who have worked eight to ten years for this moment.  Lori Glaze, NASA’s director of the Planetary Science Division, also called it an historic achievement –the culmination of advances pioneered by many other NASA missions to Mars and elsewhere and a milestone for NASA’s Mars program.… Read more

Introducing Hycean Planets

A so-called Hycean planet is one featuring large oceans and a hydrogen atmosphere. A new report from the University of Cambridge suggests this kind of planet, sized between a super-Earth and a mini-Neptunes, could potentially support life. The image features a red dwarf star as the planet’s host star. (Artist rendering by Amanda Smith, University of Cambridge)

Planets beyond our solar system, we now know, come in all shapes, sizes and consistencies.  There are rocky planets, water worlds, gaseous planets, super-Earths, hot Jupiters, tidally locked planets, planets in orbital resonance with each other,  and so much more.

A group of exoplanet researchers at the University of Cambridge have recently proposed a new category of planet, one that has seldom been considered even potentially habitable.  They call them Hycean planets due to the presence of substantial hydrogen in the atmospheres and large oceans (hydrogen and ocean = Hycean) on their surfaces.

And in an article in The Astrophysical Journal, they make the case that under certain conditions, some Hycean planets could, indeed, be habitable.

“Hycean planets open a whole new avenue in our search for life elsewhere,” said Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research.

Many of the prime Hycean candidates identified by the researchers are bigger and hotter than Earth, but the researchers argue that they still have the characteristics to host large oceans that could support microbial life similar to that found in some of Earth’s most extreme watery environments.

Hycean planets, Madhusudhan said in a release, offer a new paradigm for the search for life beyond Earth.

“Essentially, when we’ve been looking for these various molecular signatures, we have been focusing on planets similar to Earth, which is a reasonable place to start,”  he said. “But we think Hycean planets offer a better chance of finding several trace biosignatures.”

Co-author Anjali Piette, also from Cambridge, added: “It’s exciting that habitable conditions could exist on planets so different from Earth.”

An artist rendering of what a possible Hycean planet would look like.  This image is of K2-18b, which has a radius twice that of Earth and is more than eight times as massive as our planet.  The heavy hydrogen atmosphere is present, as is the red dwarf star that it orbits. (Alex Boersma)

There are no planets of this size and type in our solar system, but planets in the Hycean range are quite common in the galaxy.… Read more

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