Posted on by Shannon Hall

Novel Strategy May Help Target Extraterrestrial Intelligent Life

Photo: Mike Agliolo/Corbis

Discovering life beyond Earth might just be the holy grail of science. And even though we have yet to find evidence for little green men or blobs of bacteria, astronomers continue to search for elusive signs of life.

A novel strategy may help astronomers better target extraterrestrial intelligent life. Dr. Michael Gillon, of the University of Liege in Belgium, proposes an approach that would monitor the regions of nearby stars to search for interstellar communication devices.

The most common method in the search for extraterrestrial intelligence (abbreviated as SETI) is the use of giant radio dishes to scan the stars, listening for possible faint signals coming from distant civilizations.

While the SETI institute has been hard at work since 1959 we haven’t chanced upon a signal yet. But that doesn’t mean we’re alone or that we should stop looking.

Even without a confirmed extraterrestrial signal, most astronomers would argue that recent discoveries have strongly reinforced the hypothesis that extraterrestrial life may just be abundant in the Universe. With the help of the Kepler Space Telescope we have learned that planets are plentiful throughout the Milky Way. With most stars harboring at least one planet, it’s conceivable that a few of those planets will have the right conditions for life.

So why haven’t we detected extraterrestrial intelligent life? Why do we have this glaring Fermi Paradox — the apparent contradiction between the high probability of extraterrestrial civilizations’ existence and the lack of contact with such civilizations?

One hypotheses to explain the famous Fermi Paradox is that self-replicating probes could have explored the whole Galaxy, including our Solar System, but we just haven’t detected them yet. A self-replicating probe is one sent to a nearby planetary system where it would mine raw materials to create a replica of itself that would then head towards other nearby systems, continuing to replicate itself along the way.

While our own technological civilization is less than two hundred years old, we have already sent robotic probes to a large number of bodies in our Solar System and beyond. Our furthest-reaching probe, Voyager 1, just made it to interstellar space. But it took it over 40 years.

“We are still far from being able to build an actual self-replicating interstellar spaceship, but only because our technology is not mature enough, and not because of an obvious physical limitation,” Dr. Gillon told Universe Today.

While we cannot currently send self-replicating probes to the nearest stars in a reasonable amount of time, nothing excludes this as a reachable future project, or a project already completed by extraterrestrial intelligent life.

This study further proposes that probes from neighboring stellar systems could use the stars they orbit as gravitational lenses to communicate efficiently with each other.

The coordination of probes to explore the Galaxy would be very inefficient unless they had the ability to directly communicate with one another. The vastness and structure of the Milky Way makes this seemingly impossible. By the time a signal reached a very distant star it would be highly diluted.

However, any star is massive enough to bend and amplify light. This process, gravitational lensing, is extremely powerful. “It means that the Sun (and any other star) is an antenna much more powerful than we could ever build,” says Dr. Gillon.

Based on this method, interstellar communication devices will exist along the line that connects one star to another. We now know exactly where to look, and even where to send messages.

Could this novel idea provide a new mission for SETI?

“A negative result wouldn’t tell us very much,” explains Dr. Gillon. “But a positive result would represent one of the most important discoveries of all time.”

The paper has been accepted for publication in Acta Astronautica and is available for download here.

Posted on by Elizabeth Howell

To The Moon! Crowdfunded Solar Sail Shoots For Lunar Launch

This Lunarsail concept from the Aerospace Research and Engineering Systems Institute successfully met its crowdfunding goal and is applying to get on a NASA rocket in the next few years. Source: Kickstarter (screenshot)

It’s a tiny satellite with ambitious goals: to zip all the way from the Earth to the Moon using a solar sail. A typical “cubesat” satellite sticks around Earth’s orbit to do a science, but the team behind Lunarsail convinced dozens of crowfunding donors that their concept can go even further.

The team asked for $11,000 on Kickstarter and actually received more than $15,000. The next step is to submit a formal proposal to NASA to hitch a ride on a rocket and get into space. (An announcement of opportunity was on NASA’s website in mid-August, but the link is currently unavailable as the agency’s site is shut down amid the government furlough. The posted deadline was Nov. 26).

“Common sense seems to suggest that cubesats don’t have the power or the huge rocket they would need to reach the Moon. Common sense can be deceptive, though,” the team wrote on their crowdfunding campaign page.

NCube-2 cubesat, a typical configuration for this kind of satellite (although the outer skin is missing.) Credit: ARES Institute
NCube-2 cubesat, a typical configuration for this kind of satellite (although the outer skin is missing.) Credit: ARES Institute

“It doesn’t take a more powerful spacecraft … the satellite doesn’t care what orbit it’s in — it just does its thing. It also doesn’t require a more powerful rocket. All we need is a rocket powerful enough to put the spacecraft into an appropriate orbit around the Earth, and then we can take over and get ourselves to the Moon.”

The Aerospace Research & Engineering Systems (ARES) Institute, which is the entity behind Lunarsail, further plans to involve students in the campaign. It’s asking around to see if there are any interested parties who could “bring mission-related science activities to thousands of students, particularly those in minority and at-risk communities.” If this goes forward, students could participate through experiments, observations and also with mobile apps.

While the team acknowledges it takes time to get a concept on a rocket and into space, they have a goal of having everything “flight-ready” by December 2016. Follow updates on the project at its web page.

Posted on by Elizabeth Howell

Future Supernova Is Surrounded By Hydrogen Clouds

A "super star cluster", Westerlund 1, which is about 16,000 light-years from Earth. It can be found in the southern constellation of Ara. The picture was taken from the European Southern Observatory's VLT Survey Telescope. Credit: ESO/VPHAS+ Survey/N. Wright

The faint green glow you see in that picture is not an early harbringer of Hallowe’en spooks. It’s hydrogen gas clouds found recently nearby W26, a future supernova in the star cluster Westerlund 1.

The European Southern Observatory’s VLT Survey Telescope in Chile spotted the hydrogen in the cluster, which has hundreds of huge stars that are only believed to be a few million years old. (Our solar system, by comparison, is about 4.5 billion years old.)

“Such glowing clouds around massive stars are very rare, and are even rarer around a red supergiant— this is the first ionised nebula discovered around such a star,” the European Southern Observatory stated.

“W26 itself would be too cool to make the gas glow; the astronomers speculate that the source of the ionizing radiation may be either hot blue stars elsewhere in the cluster, or possibly a fainter, but much hotter, companion star to W26.”

Funny enough, the nebula that surrounds the red supergiant is similar to the one surrounding SN1987A, a star that exploded as a fairly bright supernova in 1987. “Studying objects like this new nebula around W26 will help astronomers to understand the mass loss processes around these massive stars, which eventually lead to their explosive demise,” ESO added.

Source: European Southern Observatory

Posted on by Carnival of Space

Carnival of Space #323

Carnival of Space. Image by Jason Major.
Carnival of Space. Image by Jason Major.

This week’s Carnival of Space is hosted by Allen Versfeld at his Urban Astronomer blog.

Click here to read Carnival of Space #323.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.

Posted on by Nancy Atkinson

Timelapse: Aurora Over Lake Michigan

A still photo taken of the aurora over Lake Michigan. Credit and copyright: Shawn Malone/Lake Superior Photo.

According to photographer Shawn Malone form Michigan, the aurora this fall have already been “insane!”

“We had a very strong auroral event here on October 2nd and 9th on Lake Superior in the Upper Peninsula of Michigan,” Malone said via email. “and what you are seeing in this video is the interaction of the solar wind impacting the magnetosphere at millions of miles per hour, that interaction causing the northern lights.”

These nights the aurora “really lit up,” said Malone.

And there could be more aurora coming soon to the northern skies: SpaceWeather.com is reporting that a coronal mass ejection propelled toward Earth by an M1-class eruption on October 13th is expected to hit our planet’s magnetic field on October. 15th. “Polar geomagnetic storms and high-latitude auroras are possible when the CME arrives,” says SpaceWeather.

Of course, not all aurora actually look like this to the human eye — you can read our article from earlier today about the reality of seeing aurorae with your eyes vs. a camera.

RADIANCE from LakeSuperiorPhoto on Vimeo.

Posted on by Nancy Atkinson

Hexacopter Drone Watches SpaceX Grasshopper Take Highest Flight Yet

Image of the Grasshopper's 325 meter hop on Jun 23, 2013. Credit: SpaceX.

This is an absolutely awesome view of the latest test flight of the SpaceX Grasshopper. The footage is shot with a camera attached to a hexacopter drone, and provides the closest view yet during a Grasshopper test of the operating rocket stage. During this test, Grasshopper flew to 744 meters (2,440 feet).

Grasshopper is a 10-story Vertical Takeoff Vertical Landing (VTVL) vehicle that SpaceX has designed to test the technologies needed to return a rocket back to Earth intact. It consists of a Falcon 9 rocket first stage tank, Merlin 1D engine, four steel and aluminum landing legs with hydraulic dampers, and a steel support structure.

While most rockets are designed to burn up in the atmosphere during reentry, SpaceX’s rockets are being designed to return to the launch pad for a vertical landing. “The Grasshopper VTVL vehicle represents a critical step towards this goal,” says SpaceX.

Sit back and enjoy the ride!

Posted on by David Dickinson

This Week’s Penumbral Lunar Eclipse and the Astronomy of Columbus

(Photo by Author)

You can always count on an eclipse to get you out of a delicate situation. Today is Columbus Day in the United States and Thanksgiving north of the border in Canada. Later this week also marks the start of the second eclipse season for 2013. Today, we thought we’d take a look at the circumstances for the first eclipse of the season kicking off this coming Friday night, October 18, as well as the fascinating role that eclipses played in the life and times of Christopher Columbus.

Friday’s event is a penumbral lunar eclipse, meaning that the Full Moon will only pass through the outer bright rim of the Earth’s shadow. Such events are subtle affairs, as opposed to total and partial lunar eclipses, which occur when the Moon enters the dark inner core, or umbra, of the Earth’s shadow. Still, you may just be able to notice a slight dusky shading on the lower southern limb of the Moon as it flirts with the umbra, barely missing it around the time of central eclipse at 23:51 Universal Time/ 7:51 PM Eastern Daylight Saving Time. Friday night’s penumbral is 3 hours and 59 minutes in duration, and 76.5% of the disk of the Moon will be immersed in the penumbra at maximum eclipse.

eclipse
The visibility footprint and circumstances of this week’s penumbral lunar eclipse. (Credit: Fred Espenak/NASA/GSFC).

Key Events occurring on Friday, October 18th:

21:50UT/5:50PM EDT: 1st contact with the Earth’s shadow.

23:51UT/7:51PM EDT: Mid-eclipse.

01:49UT(Oct 19th)/9:49PM EDT: Last contact. Eclipse ends.

The eclipse will be underway at moonrise for North and South America and occur at moonset for central Asia— Africa and Europe will see the entire eclipse. Standing on Earth’s Moon, an observer on the nearside would see a partial solar eclipse.

A simulation of Friday's lunar eclipse, looking back from Earth Moon at mid-eclipse. (Credit:
A simulation of Friday’s lunar eclipse, looking back from Moon at mid-eclipse. (Wikimedia Commons graphic in the Public Domain).

This eclipse is the 3rd and final lunar eclipse of 2013, and the 5th overall. It’s also the first in a series of four descending node eclipses, including the total lunar eclipse of October 8th next year.   It’s also the 52nd eclipse of 72 in the lunar saros series 117, which started on April 3rd, 1094 and will end with a final lunar eclipse on May 15th, 2356. Saros 117 produced its last total lunar eclipse in 1815 and its final partial in 1941.

Though penumbrals are slight events, we’ve been able to notice an appreciable difference before, during and after the eclipse photographically:

Penumbral I
Can you spy the difference? The May 18th, 2002 penumbral lunar eclipse before (left) and during mid-eclipse (right). Photos by Author.

Be sure to use identical exposure settings to catch this effect. Locations where the Moon rides high in the sky also stand the best chance of imaging the faint penumbral shading, as the Moon will be above the discoloring effects of the thicker air mass low to the horizon.

The Moon reaches descending node along the ecliptic about 20 hours after the end of the eclipse, and reaches apogee just over six days later on October 25th. The October Full Moon is also known as the Hunter’s Moon, providing a bit of extra illumination on the Fall hunt.

And this sets us up for the second eclipse of the season the next time the Moon crosses an ecliptic node, a hybrid (annular-total) solar eclipse spanning the Atlantic and Africa on November 3rd. More to come on that big ticket event soon!

In Columbus’s day, the Moon was often used to get a rough fix of a ship’s longitude at sea. Columbus was especially intrigued with the idea of using lunar eclipses to determine longitude. If you can note the position of the Moon in the sky from one location versus a known longitude during an event— such as first contact of the Moon with the Earth’s umbra during an eclipse —you can gauge your relative longitude east or west of the point. The sky moves 15 degrees, or one hour of right ascension overhead as we rotate under it. One of the earliest records of this method comes to us from Ptolemy, who deduced Alexander the Great’s position 30 degrees (2 hours) east of Carthage during the lunar eclipse of September 20th, 331 B.C. Alexander noted that the eclipse began two hours after sunset from his locale, while in Carthage it was recorded that the eclipse began at sunset.

A Jacob's crossstaff, a simple tool for measuring angles in the sky. (Photo by Author).
A Jacob’s cross staff, a simple tool for measuring angles in the sky. (Charles Towne Landing Historic Site Museum, Photo by Author).

Columbus was a student of Ptolemy, and used this method during voyages to and from the New World during the lunar eclipses of September 14th, 1494 and February 29, 1504. Of course, such a method is only approximate. The umbra of the Earth often appears ragged and indistinct on the edge of the lunar disk at the start of an eclipse, making it tough to judge the actual beginning of an eclipse by more than ten of minutes or so. And remember, you’re often watching from the pitching deck of a ship to boot!

Another problem also plagued Columbus’s navigation efforts: he favored a smaller Earth than we now know is reality. Had he listened to another Greek astronomer by the name of Eratosthenes, he would’ve gotten his measurements pretty darned close.

An eclipse also saved Columbus’s butt on one occasion. The story goes that tensions had come to a head between the locals and Columbus’s crew while stranded on the island of Jamaica in 1504. Noting that a lunar eclipse was about to occur on March 1st  (the evening of February 29th for North America), Columbus told the local leader that the Moon would rise “inflamed with wrath,” as indeed it did that night, right on schedule. Columbus then made a great show of pretending to pray for heavenly intersession, after which the Moon returned to its rightful color.  This kept a conniving Columbus and his crew stocked in supplies until a rescue ship arrived in June of that year.

A depiction of the 1504 lunar eclipse from the 1879 text Astronomie Populare by Camille Flammarion.
A depiction of the 1504 lunar eclipse from the 1879 text Astronomie Populare by Camille Flammarion.

Be sure to check out this Friday’s penumbral eclipse, and amaze your friends with the prediction of the next total lunar eclipse which occurs on U.S. Tax Day next year on April 15th, 2014. Can you do a better job of predicting your longitude than Columbus?

Posted on by Dan Majaess

Astronomers Stress the Need for Characterizing the Population of Nearby Potential Earth-Impactors

Frame grab from a video of the Feb. 15, 2013 Russian fireball by Aleksandr Ivanov

The meteor explosion over Russia in February 2013 raised concerns that even small asteroid impactors may wreak some havoc given our heavily populated cities.  A new study by NASA scientists aims to improve our understanding of such asteroids that are lurking in Earth’s vicinity.  The team, led by Amy Mainzer, noted that only a mere fraction of asteroids comparable in size to the object that exploded over Russia have been discovered, and their physical properties are poorly characterized.

The team derived fundamental properties for over a hundred near-Earth objects, and determined that many are smaller than 100 meters.  Indeed, the team notes that, “In general … [asteroids] smaller than 100-m are only detected when they are quite close … and the smallest … were detected when they were only 2-3 lunar distances away from Earth.”  

Essentially, a large fraction of these bodies may go undetected until they strike Earth, analogous to the case of the asteroid that exploded over Russia in February.

The team’s results rely partly on observations from the Wide-field Infrared Survey Explorer (WISE), which is a space-based telescope that mapped the entire sky in the mid-infrared. Observations taken in the infrared, in concert with those taken in the optical, can be used to infer the fundamental properties of asteroids (e.g., their diameter and chemical composition).

On a somewhat positive note, Mainzer remarks that 90% of near-Earth asteroids larger than 1-km are known, and those potential impactors are most worrisome as they may cause widespread fatalities.  The dinosaurs suffered a mass-extinction owing, at least in large part, to a 10-km impactor that struck Earth 65 million years ago.   However, Mainzer notes that the survey completeness drops to 25% for nearby 100-m asteroids, and it is likely to be less than 1% for 20-m asteroids like that which exploded over Russia (Chelyabinsk).  The Tunguska event (see the image below) is likewise speculated to have been on the order of that latter size.

In 1908 the Tunguska impactor toppled millions of trees in a rather remote part of Siberia. The new study by Mainzer and coauthors aimed to better characterize the population of Tunguska-sized asteroids lurking in the vicinity of the Earth.
In 1908 the Tunguska meteor explosion toppled millions of trees in a rather remote part of Siberia. A new study by Mainzer et al. 2013 characterized 100+ objects lurking in the vicinity of the Earth that are on the order of the Tunguska impactor.

The team highlights that approximately 10,000 near-Earth objects have been discovered to date, 900 of which are 1-km or larger, and 3500 objects appear to be 100-m or smaller.  “Because their small sizes usually make them undetectable until they are very nearby the Earth, it is often difficult for the current suite of asteroid surveys and follow-up telescopes to track them for very long.

Consequently, the fraction of the total population at small sizes that has been discovered to date remains very low,” noted Mainzer.

In closing, Mainzer emphasizes that, “It is, however, clear that much work remains to be done to discover and characterize the population of very small NEOs [near-Earth objects].”


The Mainzer et al. 2013 findings have been accepted for publication in the Astrophysical Journal (ApJ), and a preprint is available on arXiv.  Coauthors on the study are J. Bauer, T. Grav, J. Masiero, R. M. Cutri, E. L. Wright, C. R. Nugent, R. Stevenson, E. Clyne, G. Cukrov, and F. Masci.

Posted on by Bob King

Technicolor Auroras? A Reality Check

Beautiful red and green aurora the night of Oct. 1-2, 2013. See below for how it appeared to the eye. Details: 20mm lens, f/2.8, ISO 1600 and 25-second exposure. Credit: Bob King

I shoot a lot of pictures of the northern lights. Just like the next photographer, I thrill to the striking colors that glow from the back of my digital camera. When preparing those images for publication, many of us lighten or brighten the images so the colors and forms stand out better. Nothing wrong with that, except most times the aurora never looked that way to our eyes.

Shocked? I took the photo above and using Photoshop adjusted color and brightness to match the naked eye view. Credit: Bob King
Surprised? I took the photo above and using Photoshop adjusted color and brightness to match the naked eye view. Notice the green tinge in the bright arc at bottom. The rays were colorless. Credit: Bob King


The colors you see in aurora photos ARE real but exaggerated because the pictures are time exposures. Once the camera’s shutter opens, light accumulates on the electronic sensor, making faint and pale subjects bright and vivid. The camera can’t help it, and who would deny a photographer the chance to share the beauty? Most of us understand the magic of time exposures and factor in a mental fudge factor when looking at astronomical photos including those of the aurora.

But photos can be misleading, especially so for beginners, who might anticipate “the second coming” when they step out to watch the northern lights only to feel disappointment at the real thing. Which is too bad, because the real aurora can make your jaw drop.

A massive wall of bright purple and green rays from July 20, 2012. Details: 16mm at f/2.8, ISO 800 and 20 second exposure. Credit: Bob King
A massive wall of bright purple and green rays from July 20, 2012. Details: 16mm at f/2.8, ISO 800 and 20 second exposure. Credit: Bob King

That’s why I thought it would instructive to take a few aurora photos and tone them down to what the eye normally sees.  Truth in advertising you know. I’ve also started to include disclaimers in my captions when the images show striking crimson rays. Veteran aurora watchers know that some of the most memorable auroral displays glow blood-red, but most of the ruddy hues recorded by the camera are simply invisible to the eye. Our eyes evolved their greatest sensitivity to green light, the slice of the rainbow spectrum in which the sun shines most intensely. We’re slightly less sensitive to yellow and only a 1/10 as sensitive to red.

Image adjusted to better represent the visual view. Credit: Bob King
Image adjusted to better represent the visual view. Most auroras are between 60 and 150 miles high, but occasionally reach to 400 miles. Credit: Bob King

A typical aurora begins life as a pale white band low in the northern sky. If we’re lucky, the band intensifies, crosses the color threshold and glows pale green. Deeper and brighter greens are also common in active and bright auroras, but red is elusive because are eyes are far less sensitive to it than green. Often a curtain of green rays will be topped off by red, blue or purple emission recorded with sumptuous fidelity in the camera. What does the eye see? Smoky, colorless haze with hints of pink. Maybe.

Again, this doesn’t mean we only see green and white. I’ve watched brilliant (pale) green rays stretch from horizon to zenith with their bottoms bathed in rosy-purple, a most wonderful sight. Another factor to keep in mind is dark adaption – the longer you’ve been out under a dark sky, the more sensitive your eyes will be to whatever color might be present. At night, however, we’re mostly color blind, relying on our low-light-sensitive rod cells to get around. Cone cells, fine-tuned for color vision, are activated only when light intensity reaches certain thresholds. That happens often when it comes to auroral green but less so with other colors to which our cells are less responsive.

Excitation of oxygen and nitrogen atoms and molecules by incoming solar electrons causes them to give off specific colors shown here. Credit: NCAR
Incoming auroral electrons excite oxygen and nitrogen atoms and molecules which then shoot out photons of light at specific wavelengths when they return to their ground states. Oxygen beams light at 557.7 (green) and 603 (red) nanometers. Credit: NCAR

Auroral colors originate when electrons from the sun spiral down Earth’s magnetic field lines like firemen on a firepole and slam into oxygen and nitrogen atoms in Earth’s upper atmosphere between 60 and 150 miles (96-240 km) high. Here’s a breakdown of color, atom and altitude:

* Green – oxygen atoms 60-93 miles up (100-150 km)
* Red – oxygen atoms from 93-155 miles (150-250 km)
* Purple – molecular nitrogen up to 60 miles (100 km)
* Blue/purple – molecular nitrogen ions above 100 miles (160 km)

When an electron strikes an oxygen atom for instance, it bumps one of the oxygen’s electrons to a higher energy level. When that electron drops back down to its previous rest or ground state, it emits a photon of green light. Billions of atoms and molecules, each cranking out tiny flashes of light, make an aurora. It takes about 3/4 second for that electron to drop and the atom to release a photon before it’s given another kick from a solar electron. Most auroras are rich with oxygen emission.

The layers of our atmosphere showing the altitude of the most common auroras. Credit: Wikimedia Commons
The layers of our atmosphere showing the altitude of the most common auroras. Credit: Wikimedia Commons

Higher up, where the air’s so thin it’s identical to a hard vacuum, collisions between atoms happen only about every 7 seconds. With lots of time on their hands, oxygen electrons can transition down to their lowest energy level inside the atom, releasing a photon of red light instead of green. That’s why tall rays often show red tops especially in time exposure photos.

Only during very active geomagnetic storms, when electrons penetrate to low levels in the atmosphere, are they able to excite molecules of nitrogen, giving rise to the familiar purple fringes at the bottoms of bright rays. Bombarded molecular nitrogen ions at high altitude release a deep blue-purple light. Rarely visible to the eye, I did record it one night in the camera.

A striking coronal aurora in Feb. 1999 photographed on film. The red in this aurora was obvious to the naked eye but appeared more like the Photoshopped version at right. Credit: Bob King
A striking coronal aurora in Feb. 1999 photographed on film. The red in this aurora was obvious to the naked eye but appeared more like the Photoshopped version at right. Credit: Bob King

While videos hint at how wildly dynamic auroras can be, they’re no substitute for seeing one yourself. That’s why I never seem to get to bed when that first tempting glow appears over the northern horizon. Colorful or colorless, you’ll be astonished at how the aurora constantly re-invents itself in a multitude of forms from arcs to rays to flaming patches and writhing curlicues. Don’t miss the chance to see one. If there’s one thing that looks absolutely unearthly on this green Earth, it’s the aurora borealis. Click HERE for a guide on when and where to watch for them.

 

Posted on by Fraser Cain

Where Did the Earth’s Water Come From?

Where Did the Earth's Water Come From?

This question comes from Andrew Bumford and Steven Stormont.

In a previous episode I’ve talked about how the entire Solar System collapsed down from a cloud of hydrogen and helium left over from the Big Bang. And yet, we stand here on planet Earth, with all its water. So, how did that H20 get to our planet? The hydrogen came from the solar nebula, but where did the oxygen come from?
Here’s the amazing part.

The oxygen came from stars that lived and died before our Sun was even born. When those stars puffed out their final breaths of oxygen, carbon and other “metals”, they seeded new nebulae with the raw material for new worlds. We owe our very existence to the dead stars that came before.

When our Sun dies, it’ll give up some of its heavier elements to the next generation of stars. So, mix hydrogen together with this donated oxygen, and you’ll get H20. It doesn’t take any special process or encouragement, when those two elements come together, water is the result.

But how did it get from being spread across the early Solar System to concentrating here on Earth, and filling up our oceans, lakes and rivers? The exact mechanism is a mystery. Astronomers don’t know for sure, but there are a few theories:

Idea #1: impacts. Take a look at the craters on the Moon and you’ll see that the Solar System was a busy place, long ago. Approximately 3.8 to 4.1 billion years ago was the Late Heavy Bombardment period, when the entire inner Solar System was pummeled by asteroids. The surfaces of the planets and their moons were heated to molten slag because of the non-stop impacts. These impactors could have been comets or asteroids.

Comets are 80% water, and would deliver vast amounts of water to Earth, but they’re also volatile, and would have a difficult time surviving the harsh radiation of the young Sun. Asteroids have a lower ratio of water, but they could protect that water a little better, delivering less with each catastrophic impact.

A false-color, visible-light image of Comet ISON taken with Hubble's Wide Field Camera 3. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
A false-color, visible-light image of Comet ISON taken with Hubble’s Wide Field Camera 3. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Astronomers have also found many hybrid objects which contain large amounts of both rock and water. It’s hard to classify them either way.

Idea #2 is that large amounts of water just came directly from the solar nebula. As we orbited around the young Sun, it passed through the water-rich material in the nebula and scooped it up. Gravitational interactions between the planets would have transferred material around the Solar System, and it would have added to the Earth’s volume of water over hundreds of millions of years.

Of course, it’s entirely possible that the answer is “all of the above”. Asteroids and comets and the early solar nebula all delivered water to the Earth. Where did the Earth’s water come from? Astronomers don’t know for sure. But I’m sure glad the water is here; life here wouldn’t exist without it.