Category: Uncategorized (page 1 of 3)

What Happened to All That Water on Ancient Mars? A New Theory With a Surprising Answer

How did Mars lose the surface water that was plentiful on its surface 3 to 4 billion years ago?  New research says it did not leave the planet but rather was incorporated on a molecular level into Martian minerals.  (NASA)

Once it became clear in the past decade that the surface of ancient Mars, the inevitable question arose regarding what happened to it all since the planet is today so very dry.  And the widely-accepted answer has been that the water escaped into space, especially after the once thicker atmosphere of Mars was stripped away.

But NASA-funded research just made public has a new and bold and very different answer:  Much of the water that formed rivers, lakes and deep oceans on Mars, the research concludes, sank below the planet’s surface and is trapped inside minerals in the planet’s rocky crust.

Since early Mars is now thought to have had as much surface water as half of the the Earth’s Atlantic Ocean — enough to cover most of Mars in at least 100 meters of water — that means huge volumes of water became incorporated into the molecular structure of clays, sulfates, carbonates, opals and other hydrated minerals.

While some of the early water surely disappeared from Mars via atmospheric escape, the new findings, published in the latest issue of Science, conclude that atmospheric loss can not account for much or most of its water loss — especially now that estimates of how much water once existed on the surface of the planet have increased substantially.

“Atmospheric escape doesn’t fully explain the data that we have for how much water actually once existed on Mars,” said Eva Scheller, lead author and a doctoral candidate at the California Institute of Technology.  The rate of water loss was found to be too slow to explain what happened.

Scheller and others at Caltech set out to find other explanations. Based on modeling and data collected by Mars orbiters, rovers and from meteorites, they concluded that between 30 and 99 percent of that very early Martian surface water can now be found trapped in the minerals of the planet’s crust.

Mars mudstone, as imaged by the Curiosity rover.  (NASA/JPL-Caltech)

As described in a release for NASA’s Jet Propulsion Laboratory, the team studied the quantity of water on Mars over time in all its forms (vapor, liquid, and ice) and the chemical composition of the planet’s current atmosphere and crust through the analysis of meteorites as well as using data provided by Mars rovers and orbiters. … Read more

A Close Exoplanet Found That May Have An Atmosphere Ideal For Study

Planet Gliese 486b is close to us (in a relative sense), rocky, on the small side and may have an atmosphere.  These conclusions come from studying the planet using both the transit and radial velocity techniques, which have been the primary methods used by astronomers to find and characterize exoplanets.  Charts showing the presence of the planet using both techniques are in the blue boxes. (Render Area, Max Planck Institute for Astronomy, MPIA)

Different methods of searching for and finding distant exoplanets give different information about the planets found.

The transit method — where an exoplanets passed in front of its sun and dims the bright sunlight ever so slightly — gives astronomers not only a detection but also its radius or size.

The radial velocity method — where an exoplanet’s gravity causes its host star to “wobble” in a way that can be measured — provides different information about mass and orbit.

If a planet can be measured by both the transit and radial velocity methods, an important added dimension can be determined — how dense the planet might be.  This tells us if the planet is rocky or gaseous, watery or even if it has a central core and might have an atmosphere.  So many things have to go right that this kind of dual detection has seldom been accomplished for a  relatively small and rocky planet, but such a new planet has now been found.

The planet, Gliese 486b, is a super-Earth orbiting its host star at only 24 light-years away.  That makes the planet the third closest transiting exoplanet to Earth that is known, and the closest with a measured mass that transits a red dwarf star.

The authors of the study in the journal Science say Gliese 486b is an ideal candidate for learning how to best search for and characterize an all-important atmosphere, and to study potential habitability, too.  Future telescopes will make this kind of work more of a reality.

“Gliese 486 b is not hot enough to be a lava world,” lead author Trifon Trifonov of the Max-Planck-Institut für Astronomie and colleagues write. “But its temperature of ~700 Kelvin (800 degrees Fahrenheit) makes it suitable for emission spectroscopy and …. studies in search of an atmosphere.”

Artist impression of the surface of the newly discovered hot super-Earth Gliese 486 b. With a temperature of about 700 Kelvin (almost 800 degrees Fahrenheit), 486b possibly has an atmosphere.

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NASA’s Perseverance Rover Lands on Mars — The Third Martian Arrival in a Week

This true-color Mars globe includes Terra Meridiani, the region where NASA’s Opportunity rover explored from 2004 to 2018.  Two more Mars rovers — one from NASA and the other from China — are scheduled to land this week and then later in the year. (NASA/Greg Shirah)

Mars is receiving visitors these days.  Quite a few of them.

The most prominent visitor is NASA’s Perseverance rover,  which made a difficult but smooth precision landing at 3.55 ET  this afternoon.

The rover now sits in Jezero Crater, in an area that clearly once had lots of water flowing.   The site was selected, in part, because the Perseverance rover’s official mission includes — for the first time since the mid 1970s — an effort to find signs of long ago life.

Perseverance will join the Curiosity rover on Mars, that pioneering machine that has revolutionized our understanding of the planet since it landed in 2012  The Curiosity and Perseverance rovers are similar in design but carry different instruments with different goals.

A key difference:  Curiosity was tasked with determining whether Mars had once been habitable and found that it definitely had been, with flowing rivers, large lakes and necessary-for-life organic compounds.  Perseverance will take another scientific step forward and search for signs that Mars actually was once inhabited.

Perseverance also joins China’s Tianwen-1 (“heavenly questions”) probe,  which went into orbit around Mars last week.  It is the first Chinese spacecraft to arrive at Mars, and later this spring or summer the Chinese space agency will attempt to land a rover as well on the planet’s northern plains..

And then there’s the Hope spacecraft which entered into Mars orbit last week as well.  Launched by the United Arab Emirates, it was placed in a wide orbit so it could study the planet’s weather and climate systems, which means it also can see the full planet in one view.

These spacecraft will join several others on or orbiting Mars, making this by far the busiest time ever for exploration of Mars — a real milestone.

NASA’s Perseverance rover will land in Jezero Crater. This image was produced using instruments on NASA’s Mars Reconnaissance Orbiter, which helps identify potential landing sites for future missions. On ancient Mars, water carved channels and transported sediments to form fans and deltas within lake basins, as is clearly visible at here at Jezaro Crater (NASA/JPL-Caltech/ASU)

That the Perseverance mission has a formal goal of searching for ancient signs of life is a big deal, and involves a lot of history.… Read more

The Faint Young Sun Paradox and Mars

This NASA image of Mars at sunset taken by the Spirit  rover, evokes the conditions on early Mars when the planet received only 70 percent of the of the solar energy that it does now.  (NASA/JPL/Texas A&M/Cornell)

When our sun was young, it was significantly less luminous and sent out significantly less warming energy than it does now.  Scientists estimate that 4 million years ago, when the sun and our solar system were 500 million years old, the energy that the sun produced and dispersed was about 75 percent of what it is today.

The paradox arises because during this time of the faint young sun Earth had liquid water on its surface and — as has been conclusively proven in recent years — so did Mars, which is 61 million miles further into space.  However difficult it is to explain the faint young sun problem as it relates to early Earth, it is far more difficult to explain for far more frigid Mars.

Yet many have tried.  And because the data is both limited and innately puzzling, the subject has been vigorously debated from a variety of different perspectives.  In 2018, the journal Nature Geoscience published an editorial on the state of that dispute titled “Mars at War.”

There are numerous point of (strenuous) disagreement, with the main ones involving whether early Mars was significantly more wet and warm than previously inferred, or whether it was essentially cold and arid with only brief interludes of warming.  The differences in interpretation also require different models for how the warming occurred.

Was there a greenhouse warming  effect produced by heat-retaining molecules in the atmosphere?  Was long-term volcanic activity the cause? Or perhaps meteor strikes?  Or heat from the interior of the planet?

All of these explanations are plausible and all may have played a role.  But that begs the question that has so energized Mars scientists since Mars orbiters and the Curiosity rover conclusively proved that surface water created early rivers and valley networks, lakes and perhaps an ocean.  To solve the “faint young sun” paradox as it played out on Mars,  a climate driver (or drivers) that produces significant amounts of heat is required.

Could the necessary warming be the result of radioactive elements in the Martian crust and mantle that decay and give off impressive amounts of heat when they do?

A team led by Lujendra Ojha, an assistant professor at Rutgers University, proposes in Science Advances that may well be the answer, or at least part of the answer.… Read more

Surprising Insights Into the Asteroid Bennu’s Past, as OSIRIS-REx Prepares For a Sample-Collecting “Tag”

Artist rendering of the OSIRIS-REx spacecraft as it will approach the asteroid Bennu to collect a sample of ancient, pristine solar system material. The  pick-up”tag” is scheduled for Oct. 20. (NASA Goddard Space Flight Center, University of Arizona)

Long before there was an Earth, asteroids large and small were orbiting our young sun.  Among them was one far enough out from the sun to contain water ice, as well as organic compounds with lots of carbon.  In its five billion years or so as an object,  the asteroid was hit and broken apart by other larger asteroids, probably grew some more as smaller asteroids hit it,  and then was smashed to bits again many millions of years ago.  Some of it might have even landed on Earth.

The product of this tumultuous early history is the asteroid now called Bennu, and the destination for NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) mission.  On October 20, the spacecraft will make its dramatic final descent, will touch the ground long enough to collect some samples of the surface, and then will in the months ahead return home with its prized catch.

The sample will consist of grains of a surface that have experienced none of the ever-active geology on Earth,  no modifications caused by life,  and little of the erosion and weathering.  In other words, it will be a sample of the very early solar system from which our planet arose.

“This will be our first chance to look at an ancient, carbon-rich environment – the most pristine example of the chemistry of the very early solar system,” said Daniel Glavin, an astrobiologist at NASA’s Space Flight Center and a co-investigator of the OSIRIS-REx team.  “Anything as ancient on early Earth would have been modified many times over.”

“But at Bennu we’ll see the solar system, and the Earth,  as it was chemically before all those changes took place.  This will be the kind of pristine pre-biotic chemistry that life emerged from.”

This image of Bennu was taken by the OSIRIS-REx spacecraft from a distance of around 50 miles (80 km).
(NASA/Goddard/University of Arizona)

Bennu is an unusual asteroid.  It orbits relatively close to Earth — rather than in the main asteroid belt between Mars and Jupiter — and that’s one of several main reasons why it was selected for a visit.  It is also an asteroid with significant amounts of primeval carbon and organics, which is gold for scientists eager to understand the early solar system, planet formation and the origin of life on Earth.… Read more

Cores, Planets and The Mission to Psyche

The asteroid Psyche will be the first metal-rich celestial body to be visited by a spacecraft.  The NASA mission launches in 2022 and is expected to arrive at the asteroid in late 2026.  A central question to be answered is whether Psyche is the exposed  core of a protoplanet that was stripped of its rocky mantle. (NASA)

Deep inside the rocky planets of our solar system, as well as some solar system moons,  is an iron-based core.

Some, such as Earth’s core,  have an inner solid phase and outer molten phase, but the solar system cores studied so far are of significantly varied sizes and contain a pretty wide variety of elements alongside the iron.  Mercury, for instance, is 85 percent core by volume and made up largely of iron, while our moon’s core is thought to be 20 percent of its volume and is mostly iron with some sulfur and nickel.

Iron cores like our own play a central role in creating a magnetic field around the planet, which in turn holds in the atmosphere and may well be essential to make a planet habitable.  They are also key to understanding how planets form after a star is forged and remaining dense gases and dust are kicked out to form a protoplanetary disk, where planets are assembled.

So cores are central to planetary science, and yet they are obviously hard to study.  The Earth’s core starts about 1,800 miles below the surface, and the cores of gas giants such as Jupiter are much further inward, and even their elemental makeups are not fully understood.

All this helps explains why the upcoming NASA mission to the asteroid Psyche is being eagerly anticipated, especially by scientists who focus on planetary formation.

Scheduled to launch in 2022, the spacecraft will travel to the main asteroid belt between Mars and Jupiter and home in on what has been described as an unusual “metal body,”  which is also one of the largest asteroids orbiting the sun.

While some uncertainty remains,  it appears that Psyche is the  exposed nickel-iron core of a long-ago emerging rocky protoplanet, with the rest of the planet stripped away by collisions billions of years ago.

An artist’s impression of solar system formation, and the formation of a protoplanetary disk filled with gases and dust that over time clump together and smash into each other to form larger and larger bodies. (Gemini Observatory/AURA artwork by Lynette Cook )

That makes Psyche a most interesting place to visit.… Read more

Theorized Northern Ocean of Mars; now long gone.  (NASA)

Change is the one constant in our world– moving in ways tiny and enormous,  constructive and destructive.

We’re living now in a time when a rampaging pandemic circles the globe and when the climate is changing in so many worrisome and potentially devastating ways.

With these ominous  changes as a backdrop, it is perhaps useful to spend a moment with change as it happens in a natural world without humans.  And just how complete that change can be:

For years now, planetary scientists have debated whether Mars once had a large ocean across its northern hemisphere.

There certainly isn’t one now — the north of Mars is parched, frigid and largely featureless.  The hemisphere was largely covered over in a later epoch by a deep bed of lava, hiding signs of its past.

The northern lowlands of Mars, as photographed by the Viking 2 lander. The spacecraft landed in the Utopia Planitia section of northern Mars in 1976. (NASA/JPL)

Because our sun sent out significantly less warmth at the time of early Mars (4.2-3.5  billion years ago,) climate modelers have long struggled to come up with an explanation for how the planet — on average, 137 million miles further out than Earth — could have been anything but profoundly colder than today. And if that world was so unrelentingly frigid, how could there be a surface ocean of liquid water?

But discoveries in the 21st century have strongly supported the long-ago presence of water on a Mars in the form of river valleys, lakes and a water cycle to feed them.  The work done by the Curiosity rover and Mars-orbiting satellites has made this abundantly clear.

An ocean in the northern lowlands is one proposal made to explain how the water cycle was fed.

And now, In a new paper in Journal of Geophysical Research: Planets,  scientists from Japan and the United States have presented modelling and analysis describing how and why Mars had to have a large ocean early in its history to produce the geological landscape that is being found.

Lead author Ramses Ramirez, a planetary scientist with the Earth-Life Science Institute in Tokyo, said it was not possible to determine how long the ocean persisted, but their team concluded that it had to be present  in that early period around 4 billion to 3.5 billion years ago.  That is roughly when what are now known to be river valleys were cut in the planet’s southern highlands.… Read more

Exploring Our Sun Will Help Us Understand Habitability

The surface of the sun, with each “kernel” or “cell” roughly the size of Texas. The movie is made up of images produced by the Daniel Inouye SolarTelescope in Hawaii.  Novel and even revolutionary data and images are also expected from the Parker Solar Probe (which will travel into the sun’s atmosphere, or corona) and the just launched Solar Orbiter, which will study (among many other things) the sun’s polar regions. (NSO/NSF/AURA)

 

Scientists have been  studying our sun for centuries, and at this point know an awful lot about it — the millions of degrees Fahrenheit heat that it radiates out from the corona, the tangled and essential magnetic fields that it creates, the million-miles-per-hour solar wind and the charged high-energy solar particles that can be so damaging to anything alive.

But we have now entered a time when solar science is taking a major leap forward with the deployment of three pioneering instruments that will explore the sun and its surroundings as never before.  One is a space telescopes that will get closer to the sun (by far) than any probe before, another is a probe that will make the first observations of the sun’s poles, and the third is a ground-based solar telescope that can resolve the sun in radically new ways — as seen in the image above, released last month.

Together, NASA’s Parker Solar Probe, the joint European Space Agency-NASA Solar Orbiter mission and the National Science Foundation’s Inouye Solar Telescope on Hawai’i will provide pathways to understand some of the mysteries of the sun.  They include resolving practical issues involving the dynamics  of “space weather” that can harm astronauts and telecommunications systems, and larger theoretical unknowns related to all the material that stars scatter into space and onto planets.

Some of those unresolved questions include determining how and why heat and energy flow from the sun’s inner core to the outer corona and make it so much hotter, determining the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind, the make-up and effects of solar flares and coronal mass ejections, and how and why the sun is able to create and control the heliosphere — the vast bubble of charged particles blown by the solar wind into interstellar space.

 

An illustration of Kepler2-33b, , one of the youngest exoplanets detected to date using NASA Kepler Space Telescope.

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On The Rugged Frontier Of The Hunt For Signs Of Life On Early Earth And Ancient Mars

The vigorously debated finding from the Isua greenstone or supercrustal belt, a 1,200-square-mile area of ancient rocks in Greenland.  Proponents say the rises, from .4 to 1.6 inches tall, are  biosignatures of bacteria and sediment mounds that made up stromatolites almost 3.8 billion years ago.  Critics say additional testing has shown they are the result of non-biological forces.  (Nature and Nutman et al.)

Seldom does one rock outcrop get so many visitors in a day, especially when that outcrop is located in rugged, frigid terrain abutting the Greenland Ice Sheet and can be reached only by helicopter.

But this has been a specimen of great importance and notoriety since it appeared from beneath the snow pack some eight years ago. That’s when it was first identified by two startled geologists as something very different from what they had seen in four decades of scouring the geologically revelatory region – the gnarled Isua supercrustal belt – for fossil signs of very early life.

Since that discovery the rock outcrop has been featured in a top journal and later throughout the world as potentially containing the earliest signature of life on Earth – the outlines of half inch to almost two inch-high stromatolite structures between 3.7 and 3.8 billion years old.

The Isua greenstone, or supracrustal belt contains some of the oldest known rocks and outcrops in the world, and is about 100 miles northeast of the capital, Nuuk.

If Earth could support the life needed to form primitive but hardly uncomplicated stromatolites that close to the initial cooling of the planet, then the emergence of life might not be so excruciatingly complex after all. Maybe if the conditions are at all conducive for life on a planet (early Mars comes quickly to mind) then life will probably appear.

Extraordinary claims in science, however, require extraordinary proof, and inevitably other scientists will want to test the claims.

Within two years of that initial ancient stromatolite splash in a Nature paper (led by veteran geologist Allen Nutman of the University of Wollongong in Australia), the same journal published a study that disputed many of the key observations and conclusions of the once-hailed ancient stromatolite discovery.  The paper concluded the outcrop had no signs of early life at all.

Debates and disputes are common in geology as the samples get older,  and especially in high profile science with important implications.  In this case, the implications of what is in the rocks reach into the solar system and the cosmos. … Read more

Exoplanets Discoveries Flood in From TESS

NASA’s Transiting Exoplanet Survey Satellite (TESS) has hundreds of “objects of interest” waiting to be confirmed as planets in the data from the space telescope’s four cameras.  These three were the first confirmed TESS discoveries, identified last year during its first three months of observing. By the time the mission is done, TESS’s wide-field cameras will have covered the whole sky in search of transiting exoplanets around 200,000 of the nearest (and brightest) stars. (NASA / MIT / TESS)

The newest space telescope in the sky — NASA’s Transiting Exoplanet Survey Satellite, TESS — has been searching for exoplanets for less than a year, but already it has quite a collection to its name.

The TESS mission is to find relatively nearby planets orbiting bright and stable suns, and so expectations were high from the onset about the discovery of important new planets and solar systems.  At a meeting this week at the Massachusetts Institute of Technology devoted to TESS  results,  principal investigator George Ricker pronounced the early verdict.

The space telescope, he said,  “has far exceeded our most optimistic hopes.”  The count is up to 21 new planets and 850 additional  candidate worlds waiting to be confirmed.

Equally or perhaps more important is that the planets and solar systems being discovered promise important results.  They have not yet included any Earth-sized rocky planet in a sun’s habitable zone — what is generally considered the most likely, though hardly the only, kind of planet to harbor life — but they did include planets that offer a great deal when it comes to atmospheres and how they can be investigated.

This infographic illustrates key features of the TOI 270 system, located about 73 light-years away in the southern constellation Pictor. The three known planets were discovered by NASA’s Transiting Exoplanet Survey Satellite through periodic dips in starlight caused by each orbiting world. Insets show information about the planets, including their relative sizes, and how they compare to Earth. Temperatures given for TOI 270’s planets are equilibrium temperatures, (NASA’s Goddard Space Flight Center/Scott Wiessinger)

One of the newest three-planet system is called TOI-270, and it’s about 75 light years from Earth. The star at the center of the system is a red dwarf, a bit less than half the size of the sun.

Despite its small size, it’s brighter than most of the nearby stars we know host planets. And it’s stable, making its solar system especially valuable.

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