Earth is our Solar System’s bluest planet, and yet no one really knows where all our water came from.
The dust of a nearby asteroid has now revealed a potentially overlooked source: the Sun.
Some water on our planet, it seems, might have been created by a river of charged particles, blown from the upper atmosphere of the Sun billions of years ago.
When solar wind interacts with the tiny dust particles found on certain asteroids, it can create a small amount of water, and this could explain some of the liquid we find here on our planet.
Most modern models suggest the majority of H20 on Earth originally came from an extraterrestrial source, possibly from C-type asteroids in the Jupiter-Saturn region and beyond.
These far-away asteroids are thought to be the parent bodies of carbonaceous chondrite meteorites that regularly crash into Earth, and this particular type of meteorite is known to contain a significant amount of water-containing minerals.
But carbonaceous chondrites probably aren’t the only way water was initially delivered to Earth. Other types of water-rich meteorites could have also done the same, especially since carbonaceous chondrites can’t account for Earth’s entire water budget.
There are other types of chondrite asteroids that could have also held particles of water, albeit to a lesser extent. The near-Earth asteroid, Itokawa, for instance, is an ordinary chondrite asteroid, and an analysis of samples taken from this silicate-rich rock in 2010 found signs of water, and the source could very well be the Sun.
Solar wind irradiation has been proposed in the past as a possible way to form water on silicate-rich materials floating in space.
In the lab, volatile hydrogen ions have been shown to react with silicate minerals, resulting in water as a byproduct, and electron microscopy and electron spectroscopy studies have found direct evidence of H20 within extraterrestrial dust particles in the past.
Theoretically, if water becomes trapped in these dust particles, the element will be protected from space weathering and can then be delivered via meteorites to other bodies in space.
“This phenomenon could explain why the regoliths of airless worlds such as the Moon, which were once thought to be anhydrous, contain several percent H20,” the authors of the new study explain.
To explore this hypothesis further and in a slightly different way, researchers turned to the S-type asteroid, Itokawa, to see if this object contains a ‘volatile reservoir’ of isotypes similar to that of solar wind.
While most water isotypes on Earth match carbonaceous chondrites, a small percentage don’t, and the Sun or the solar nebula have been proposed as possible sources.
Imagine, having to swim your way everywhere, probably, having a blubber, and communicate like a whale. Imagine how life would have been in a water world.
According to a new analysis of the features of Earth’s mantle over its long history, our whole world was once engulfed by a vast ocean, with very few or no land masses at all. It was an extremely soggy space rock.
So where the heck did all the water go? According to a team of researchers led by planetary scientist Junjie Dong of Harvard University, minerals deep inside the mantle slowly drunk up ancient Earth’s oceans to leave what we have today.
“We find that water storage capacity in a hot, early mantle may have been smaller than the amount of water Earth’s mantle currently holds, so the additional water in the mantle today would have resided on the surface of the early Earth and formed bigger oceans.
“Our results suggest that the long‐held assumption that the surface oceans’ volume remained nearly constant through geologic time may need to be reassessed.”
The scientists focused on different types of oxygen that seawater had carried into the crust. In particular, they analysed the relative amounts of two isotopes, oxygen-16 and the ever-so-slightly-heavier oxygen-18, in more than 100 samples of the stone.
They found that seawater contained more oxygen-18 when the crust was formed 3.2bn years ago. The most likely explanation, they believe, is that Earth had no continents at the time, because when these form, the clays they contain absorb the ocean’s heavy oxygen isotopes.
“Without continents above the ocean, the oxygen value would be distinct from today, which is exactly what we found,” Johnson said. “And it’s different in a way that’s most easily explained without land to get rained on and without soil formation.”
Earth is thought to have been born in an interplanetary desert, too close to the sun for water ice to survive. Many researchers suspect that ocean water got delivered toward the end of Earth’s formation by ice-laden asteroids that wandered in from cooler, more distant regions of the solar system (SN: 5/6/15). But the ocean isn’t the planet’s largest water reservoir. Researchers estimate that Earth’s interior holds several times as much water as is found at the surface.
To test whether or not the material that formed Earth could have delivered this deep water, cosmochemist Laurette Piani of the University of Lorraine in Vandœuvre-lès-Nancy, France, and colleagues analyzed meteorites known as enstatite chondrites. Thanks to many chemical similarities with Earth rocks, these relatively rare meteorites are widely thought to be good analogs of the dust and space rocks from the inner solar system that formed Earth’s building blocks, Piani says.
Several years ago, planetary scientist Lynnae Quick began to wonder whether any of the more than 4,000 known exoplanets, or planets beyond our solar system, might resemble some of the watery moons around Jupiter and Saturn. Though some of these moons don’t have atmospheres and are covered in ice, they are still among the top targets in NASA’s search for life beyond Earth. Saturn’s moon Enceladus and Jupiter’s moon Europa, which scientists classify as “ocean worlds,” are good examples.
“Plumes of water erupt from Europa and Enceladus, so we can tell that these bodies have subsurface oceans beneath their ice shells, and they have energy that drives the plumes, which are two requirements for life as we know it,” says Quick, a NASA planetary scientist who specializes in volcanism and ocean worlds. “So if we’re thinking about these places as being possibly habitable, maybe bigger versions of them in other planetary systems are habitable too.”
Quick, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, decided to explore whether—hypothetically—there are planets similar to Europa and Enceladus in the Milky Way galaxy. And, could they, too, be geologically active enough to shoot plumes through their surfaces that could one day be detected by telescopes.
Through a mathematical analysis of several dozen exoplanets, including planets in the nearby TRAPPIST-1 system, Quick and her colleagues learned something significant: More than a quarter of the exoplanets they studied could be ocean worlds, with a majority possibly harboring oceans beneath layers of surface ice, similar to Europa and Enceladus. Additionally, many of these planets could be releasing more energy than Europa and Enceladus.
Scientists may one day be able to test Quick’s predictions by measuring the heat emitted from an exoplanet or by detecting volcanic or cryovolcanic (liquid or vapor instead of molten rock) eruptions in the wavelengths of light emitted by molecules in a planet’s atmosphere. For now, scientists cannot see many exoplanets in any detail. Alas, they are too far away and too drowned out by the light of their stars. But by considering the only information available—exoplanet sizes, masses and distances from their stars—scientists like Quick and her colleagues can tap mathematical models and our understanding of the solar system to try to imagine the conditions that could be shaping exoplanets into livable worlds or not.
While the assumptions that go into these mathematical models are educated guesses, they can help scientists narrow the list of promising exoplanets to search for conditions favorable to life so that NASA’s upcoming James Webb Space Telescope or other space missions can follow up.
“Future missions to look for signs of life beyond the solar system are focused on planets like ours that have a global biosphere that’s so abundant it’s changing the chemistry of the whole atmosphere,” says Aki Roberge, a NASA Goddard astrophysicist who collaborated with Quick on this analysis. “But in the solar system, icy moons with oceans, which are far from the heat of the Sun, still have shown that they have the features we think are required for life.”
To look for possible ocean worlds, Quick’s team selected 53 exoplanets with sizes most similar to Earth, though they could have up to eight times more mass. Scientists assume planets of this size are more solid than gaseous and, thus, more likely to support liquid water on or below their surfaces. At least 30 more planets that fit these parameters have been discovered since Quick and her colleagues began their study in 2017, but they were not included in the analysis, which was published on June 18 in the journal Publications of the Astronomical Society of the Pacific.
With their Earth-size planets identified, Quick and her team sought to determine how much energy each one could be generating and releasing as heat. The team considered two primary sources of heat. The first, radiogenic heat, is generated over billions of years by the slow decay of radioactive materials in a planet’s mantle and crust. That rate of decay depends on a planet’s age and the mass of its mantle. Other scientists already had determined these relationships for Earth-size planets. So, Quick and her team applied the decay rate to their list of 53 planets, assuming each one is the same age as its star and that its mantle takes up the same proportion of the planet’s volume as Earth’s mantle does.
Next, the researchers calculated heat produced by something else: tidal force, which is energy generated from the gravitational tugging when one object orbits another. Planets in stretched out, or elliptical, orbits shift the distance between themselves and their stars as they circle them. This leads to changes in the gravitational force between the two objects and causes the planet to stretch, thereby generating heat. Eventually, the heat is lost to space through the surface.
One exit route for the heat is through volcanoes or cryovolcanoes. Another route is through tectonics, which is a geological process responsible for the movement of the outermost rocky or icy layer of a planet or moon. Whichever way the heat is discharged, knowing how much of it a planet pushes out is important because it could make or break habitability.
For instance, too much volcanic activity can turn a livable world into a molten nightmare. But too little activity can shut down the release of gases that make up an atmosphere, leaving a cold, barren surface. Just the right amount supports a livable, wet planet like Earth, or a possibly livable moon like Europa.
In the next decade, NASA’s Europa Clipper will explore the surface and subsurface of Europa and provide insights about the environment beneath the surface. The more scientists can learn about Europa and other potentially habitable moons of our solar system, the better they’ll be able to understand similar worlds around other stars—which may be plentiful, according to today’s findings.
“Forthcoming missions will give us a chance to see whether ocean moons in our solar system could support life,” says Quick, who is a science team member on both the Clipper mission and the Dragonfly mission to Saturn’s moon Titan. “If we find chemical signatures of life, we can try to look for similar signs at interstellar distances.”
When Webb launches, scientists will try to detect chemical signatures in the atmospheres of some of the planets in the TRAPPIST-1 system, which is 39 light years away in the constellation Aquarius. In 2017, astronomers announced that this system has seven Earth-size planets. Some have suggested that some of these planets could be watery, and Quick’s estimates support this idea. According to her team’s calculations, TRAPPIST-1 e, f, g and h could be ocean worlds, which would put them among the 14 ocean worlds the scientists identified in this study.
The researchers predicted that these exoplanets have oceans by considering the surface temperatures of each one. This information is revealed by the amount of stellar radiation each planet reflects into space. Quick’s team also took into account each planet’s density and the estimated amount of internal heating it generates compared to Earth.
“If we see that a planet’s density is lower than Earth’s, that’s an indication that there might be more water there and not as much rock and iron,” Quick says. And if the planet’s temperature allows for liquid water, you’ve got an ocean world.
“But if a planet’s surface temperature is less than 32 degrees Fahrenheit (0 degrees Celsius), where water is frozen,” Quick says, “then we have an icy ocean world, and the densities for those planets are even lower.”
The World Health Organization (WHO) has called for a reduction in plastic pollution to benefit the environment and reduce human exposure.
WHO launched its first report today on microplastics in drinking-water, cautioning the that while findings show a low risk to human health, more research is needed.
treated tap and bottled water have raised questions and concerns about the impact that microplastics in drinking-water might have on human health.
WHO notes that the report critically examines the evidence related to the occurrence of microplastics in the water cycle (including both tap and bottled drinking-water and its sources), the potential health impacts from microplastic exposure and the removal of microplastics during wastewater and drinking-water treatment.
“Recommendations are made with respect to monitoring and management of microplastics and plastics in the environment, and to better assess human health risks and inform appropriate management actions, a number of key knowledge gaps are identified.”
“We urgently need to know more about the health impact of microplastics because they are everywhere – including in our drinking-water,” says Dr Maria Neira, Director, Department of Public Health, Environment and Social Determinants of Health, at WHO. “Based on the limited information we have, microplastics in drinking water don’t appear to pose a health risk at current levels. But we need to find out more. We also need to stop the rise in plastic pollution worldwide.”
According to the analysis, which summarizes the latest knowledge on microplastics in drinking-water, microplastics larger than 150 micrometres are not likely to be absorbed in the human body and uptake of smaller particles is expected to be limited. Absorption and distribution of very small microplastic particles including in the nano size range may, however, be higher, although the data is extremely limited.
The Pan African University Institute for Water and Energy Sciences including Climate Change (PAUWES) (www.PAUWES.dz) celebrated the third graduating class of both the engineering and policy tracks of it Masters programmes in Water and Energy.
The graduating class made up of 79 students from across the African continent, received their diplomas during a ceremony at the University of Tlemcen. The graduating students and their guests were addressed by official representatives and dignitaries from the Algerian government from across Africa and Europe, including Her Excellency Prof. Sarah Anyang Agbor, the African Union Commissioner for Human Resources, Science and Technology (HRST), Mr. Ali Benyaiche, the Governor of the Wilaya of Tlemcen, and Her Excellency Ulrike Knotz, the German Ambassador to Algeria.
This year’s graduating students are about to constitute the next generation of engineers and policymakers committed to addressing the issues critical to Africa’s sustainable development. PAUWES graduates have not only successfully completed their coursework requirements, they have conducted practice-oriented research for their master theses that address the water, energy, and climate change challenges facing Africa and elsewhere. Additionally, they completed international internships in the private and public sectors at renowned research institutions across Africa and beyond, gaining a transcontinental perspective of those same challenges. During the graduation ceremony, H.E. Prof. Sarah ANYANG AGBOR said: “I would like to congratulate you on your efforts and for upholding the core values of our continent. I wish you the best in your future endeavours. As a mother, let me advise you to always remember that in real life, every day you graduate. Graduation is a process that goes on until the last day of your life. So always strive to graduate in every decision or activity you make. I am proud of you, we are proud of You, Africa is proud of You!”.
The graduating cohort represents and fulfils one of the key objectives of the Pan African University (PAU) and PAUWES—which is to foster an African learning environment of the most qualified and motivated scholars while revitalising and nurturing the quality of African higher education. The Class of 2018 has students from twenty African Union member states with all regions of the African continent represented. This diverse cohort of students have had the opportunity to study, being taught by and international faculty coming from four continents. Supported by the University of Tlemcen and the key thematic partner Germany, Prof. Abdellatif Zerga, Director of PAUWES, is confident: “The students of the Class of 2018 are well positioned to become change makers in public administration, policy-making, research, technology, private enterprise, and civil society.” The PAUWES 2018 Class Booklet(https://bit.ly/2OX87vn) showcases this year’s graduates, and PAUWES is pleased to invite future employers to meet them.
PAUWES has also just welcomed the incoming class (students from 29 countries across Africa) and is proud to announce that thanks to a number of specific measures, gender parity could be reached, which is a huge achievement within our latest cohort.