Posted on by Matt Williams

Earth and Venus are the Same Size, so Why Doesn’t Venus Have a Magnetosphere? Maybe it Didn’t Get Smashed Hard Enough

At a closest average distance of 41 million km (25,476,219 mi), Venus is the closest planet to Earth. Credit: NASA/JPL/Magellan

For many reasons, Venus is sometimes referred to as “Earth’s Twin” (or “Sister Planet”, depending on who you ask). Like Earth, it is terrestrial (i.e. rocky) in nature, composed of silicate minerals and metals that are differentiated between an iron-nickel core and silicate mantle and crust. But when it comes to their respective atmospheres and magnetic fields, our two planets could not be more different.

For some time, astronomers have struggled to answer why Earth has a magnetic field (which allows it to retain a thick atmosphere) and Venus do not. According to a new study conducted by an international team of scientists, it may have something to do with a massive impact that occurred in the past. Since Venus appears to have never suffered such an impact, its never developed the dynamo needed to generate a magnetic field.

The study, titled “Formation, stratification, and mixing of the cores of Earth and Venus“, recently appeared in the scientific journal Earth and Science Planetary Letters. The study was led by Seth A. Jacobson of Northwestern University, and included members from the Observatory de la Côte d’Azur, the University of Bayreuth, the Tokyo Institute of Technology, and the Carnegie Institution of Washington.

The Earth's layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com

For the sake of their study, Jacobson and his colleagues began considering how terrestrial planets form in the first place. According to the most widely-accepted models of planet formation, terrestrial planets are not formed in a single stage, but from a series of accretion events characterized by collisions with planetesimals and planetary embryos – most of which have cores of their own.

Recent studies on high-pressure mineral physics and on orbital dynamics have also indicated that planetary cores develop a stratified structure as they accrete. The reason for this has to do with how a higher abundance of light elements are incorporated in with liquid metal during the process, which would then sink to form the core of the planet as temperatures and pressure increased.

Such a stratified core would be incapable of convection, which is believed to be what allows for Earth’s magnetic field. What’s more, such models are incompatible with seismological studies that indicate that Earth’s core consists mostly of iron and nickel, while approximately 10% of its weight is made up of light elements – such as silicon, oxygen, sulfur, and others. It’s outer core is similarly homogeneous, and composed of much the same elements.

As Dr. Jacobson explained to Universe Today via email:

“The terrestrial planets grew from a sequence of accretionary (impact) events, so the core also grew in a multi-stage fashion. Multi-stage core formation creates a layered stably stratified density structure in the core because light elements are increasingly incorporated in later core additions. Light elements like O, Si, and S increasingly partition into core forming liquids during core formation when pressures and temperatures are higher, so later core forming events incorporate more of these elements into the core because the Earth is bigger and pressures and temperatures are therefore higher.

“This establishes a stable stratification which prevents a long-lasting geodynamo and a planetary magnetic field. This is our hypothesis for Venus. In the case of Earth, we think the Moon-forming impact was violent enough to mechanically mix the core of the Earth and allow a long-lasting geodynamo to generate today’s planetary magnetic field.”

To add to this state of confusion, paleomagnetic studies have been conducted that indicate that Earth’s magnetic field has existed for at least 4.2 billion years (roughly 340 million years after it formed). As such, the question naturally arises as to what could account for the current state of convection and how it came about. For the sake of their study, Jacobson and his team considering the possibility that a massive impact could account for this. As Jacobson indicated:

“Energetic impacts mechanically mix the core and so can destroy stable stratification. Stable stratification prevents convection which inhibits a geodynamo. Removing the stratification allows the dynamo to operate.”

Basically, the energy of this impact would have shaken up the core, creating a single homogeneous region within which a long-lasting geodynamo could operate. Given the age of Earth’s magnetic field, this is consistent with the Theia impact theory, where a Mars-sized object is believed to have collided with Earth 4.51 billion years ago and led to the formation of the Earth-Moon system.

This impact could have caused Earth’s core to go from being stratified to homogeneous, and over the course of the next 300 million years, pressure and temperature conditions could have caused it to differentiate between a solid inner core and liquid outer core. Thanks to rotation in the outer core, the result was a dynamo effect that protected our atmosphere as it formed.

Artist’s concept of a collision between proto-Earth and Theia, believed to happened 4.5 billion years ago. Credit: NASA

The seeds of this theory were presented last year at the 47th Lunar and Planetary Science Conference in The Woodlands, Texas. During a presentation titled “Dynamical Mixing of Planetary Cores by Giant Impacts“, Dr. Miki Nakajima of Caltech – one of the co-authors on this latest study – and David J. Stevenson of the Carnegie Institution of Washington. At the time, they indicated that the stratification of Earth’s core may have been reset by the same impact that formed the Moon.

It was Nakajima and Stevenson’s study that showed how the most violent impacts could stir the core of planets late in their accretion. Building on this, Jacobson and the other co-authors applied models of how Earth and Venus accreted from a disk of solids and gas about a proto-Sun. They also applied calculations of how Earth and Venus grew, based on the chemistry of the mantle and core of each planet through each accretion event.

The significance of this study, in terms of how it relates to the evolution of Earth and the emergence of life, cannot be understated. If Earth’s magnetosphere is the result of a late energetic impact, then such impacts could very well be the difference between our planet being habitable or being either too cold and arid (like Mars) or too hot and hellish (like Venus). As Jacobson concluded:

“Planetary magnetic fields shield planets and life on the planet from harmful cosmic radiation. If a late, violent and giant impact is necessary for a planetary magnetic field then such an impact may be necessary for life.”

Looking beyond our Solar System, this paper also has implications in the study of extra-solar planets. Here too, the difference between a planet being habitable or not may come down to high-energy impacts being a part of the system’s early history. In the future, when studying extra-solar planets and looking for signs of habitability, scientists may very well be forced to ask one simple question: “Was it hit hard enough?”

Further Reading: Earth Science and Planetary Letters

Posted on by Matt Williams

New Study Says Earth Avoided a “Carbon Overdose” During Formation

A new study from the University of Heidelberg suggests that flash-heating and carbon depletion could have been intrinsic to the emergence and evolution of life on Earth. Credit: NASA

According to the Nebular Hypothesis, the Sun and planets formed 4.6 billion years ago from a giant cloud of dust and gas. This began with the Sun forming in the center, and the remaining material forming a protoplanetary disc, from which the planets formed. Whereas the planets in the outer Solar System were largely made up of gases (i.e. the Gas Giants), those closer to the Sun formed from silicate minerals and metals (i.e. the terrestrial planets).

Despite having a pretty good idea of how this all came about, the question of exactly how the planets of the Solar System formed and evolved over the course of billions of year is still subject to debate. In a new study, two researchers from the University of Heidelberg considered the role played by carbon in both the formation of Earth and the emergence and evolution of life.

Their study, “Spatial Distribution of Carbon Dust in the Early Solar Nebula and the Carbon Content of Planetesimals“, recently appeared in the journal Astronomy and Astrophysics. The study was conducted by Hans-Peter Gail, from the Institute for Theoretical Astrophysics at the University of Heidelberg, and Mario Trieloff – from Heidelberg’s Institute of Earth Sciences and the Klaus-Tschira-Laboratory for Cosmochemistry.

A slice of the Allende meteorite with silicate globules of the size of a millimetre. Credit: Institute of Earth Science

For the sake of their study, the pair considered what role the element carbon – which is essential to life here on Earth – played in planetary formation. Essentially, scientists are of the opinion that during the earliest days of the Solar System – when it was still a giant cloud of dust and gas – carbon-rich materials were distributed to the inner Solar System from the outer Solar System.

Out beyond the “Frost Line” – where volatiles like water, ammonia and methane and are able to condense into ice – bodies containing frozen carbon compounds formed. Much like how water was distributed throughout the Solar System, that these bodies were supposedly kicked out of their orbits and sent towards the Sun, distributing volatile materials to the planetesimals that would eventually grow to become the terrestrial planets.

However, when one compares the kinds of meteors that distributed primordial material to Earth – aka. chondrite meteorites –  one notices a certain discrepancy. Basically, carbon is comparatively rare on Earth compared to these ancient rocks, the reason for which has remained a mystery. As Prof. Trieloff, who was the co-author on the study, explained in a University of Heidelberg press release:

“On Earth, carbon is a relatively rare element. It is enriched close to the Earth´s surface, but as a fraction of the total matter on Earth it is a mere one-half of 1/1000th. In primitive comets, however, the proportion of carbon can be ten percent or more.”

Artist’s conception of a solar system in formation. Credit: NASA/FUSE/Lynette Cook

“A substantial portion of the carbon in asteroids and comets is in long-chain and branched molecules that evaporate only at very high temperatures,” added Dr. Grail, the study’s lead author. “Based on the standard models that simulate carbon reactions in the solar nebula where the sun and planets originated, the Earth and the other terrestrial planets should have up to 100 times more carbon.”

To address this, the two researches constructed a model that assumed that short-duration flash-heating events – where the Sun heated the protoplanetary disc – were responsible for this discrepancy. They also assumed that all matter in the inner Solar System was heated to temperatures of between 1,300 and 1,800 °C (2372 to 3272 °F) before small planetesimals and terrestrial planets eventually formed.

Dr. Grail and Trieloff believe the evidence for this lies in the round grains in meteorites that form from molten droplets – known as chondrules. Unlike chondrite meteorites, which can be composed of up to a few percent carbon, chondrules are largely depleted of this element. This, they claim, was the a result of the same flash-heating events that took place before the chondrules could accrete to form meteorites. As Dr. Gail indicated:

“Only the spikes in temperature derived from the chondrule formation models can explain today’s low amount of carbon on the inner planets. Previous models did not take this process into account, but we apparently have it to thank for the correct amount of carbon that allowed the evolution of the Earth’s biosphere as we know it.”

Artist impression of the Late Heavy Bombardment period. Credit: NASA

In short, the discrepancy between the amount of carbon found in chondritic-rock material and that found on Earth can be explained by intense heating in the primordial Solar System. As Earth formed from chrondritic material, the extreme heat caused it to be depleted of its natural carbon. In addition to shedding light on what has been an ongoing mystery in astronomy, this study also offers new insight into how life in the Solar System began.

Basically, the researchers speculate that the flash-heating events in the inner Solar System may have been necessary for life here on Earth. Had there been too much carbon in the primordial material that coalesced into our planet, the result could have been a “carbon overdose”. This is because when carbon becomes oxidized, it forms carbon dioxide, a major greenhouse gas that can lead to a runaway heating effect.

This is what planetary scientists believe happened to Venus, where the presence of abundant CO2 – combined with its increased exposure to Solar radiation – led to the hellish environment that is there today. But on Earth, CO2 was removed from the atmosphere by the silicate-carbonate cycle, which allowed for Earth to achieve a balanced and life-sustaining environment.

“Whether 100 times more carbon would permit effective removal of the greenhouse gas is questionable at the very least,” said Dr. Trieloff. “The carbon could no longer be stored in carbonates, where most of the Earth’s CO2 is stored today. This much CO2 in the atmosphere would cause such a severe and irreversible greenhouse effect that the oceans would evaporate and disappear.”

Artist’s impression of the “Venus-like” exoplanet in a nearby star system. Credit: cfa.harvard.edu

It is a well-known fact that life here on Earth is carbon-based. However, knowing that conditions during the early Solar System prevented an overdose of carbon that could have turned Earth into a second Venus is certainly interesting. While carbon may be essential to life as we know it, too much can mean the death of it. This study could also come in handy when it comes to the search for life in extra-solar systems.

When examining distant stars, astronomers could ask, “were primordial conditions hot enough in the inner system to prevent a carbon overdose?” The answer to that question could be the difference between finding an Earth 2.0, or another Venus-like world!

Further Reading: University of Heidelberg, Astronomy and Astrophysics

Posted on by Matt Williams

New Study Sheds Light on How Earth and Mars Formed

Snapshot of a computer simulation of two (relatively small) planets colliding with each other. The colors show how the rock of the impacting body (dark grey, in center of impact area) accretes to the target body (rock; light grey), while some of the rock in the impact area is molten (yellow to white) or vaporised (red). Credit: Philip J. Carter

In accordance with the Nebular Hypothesis, the Solar System is believed to have formed through the process of accretion. Essentially, this began when a massive cloud of dust and gas (aka. the Solar Nebula) experienced a gravitational collapse at its center, giving birth to the Sun. The remaining dust and gas then formed into a protoplanetary disc around the Sun, which gradually coalesced to form the planets.

However, much about the process of how planets evolved to become distinct in their compositions has remained a mystery. Luckily, a new study by a team of researchers from the University of Bristol has approached the subject with a fresh perspective. By examining a combination of Earth samples and meteorites, they have shed new light on how planets like Earth and Mars formed and evolved.

The study, titled “Magnesium Isotope Evidence that Accretional Vapour Loss Shapes Planetary Compositions“, recently appeared in the scientific journal Nature. Led by Remco C. Hin, a senior research associate from the School of Earth Sciences at the University of Bristol, the team compared samples of rock from Earth, Mars, and the Asteroid Vesta to compare the levels of magnesium isotopes within them.

Artist’s impression of the early Solar System, where collision between particles in an accretion disc led to the formation of planetesimals and eventually planets. Credit: NASA/JPL-Caltech

Their study attempted answering what has been a lingering question in the scientific community – i.e. did the planets form the way they are today, or did they acquire their distinctive compositions over time? As Dr. Remco Hin explained in a University of Bristol press release:

“We have provided evidence that such a sequence of events occurred in the formation of the Earth and Mars, using high precision measurements of their magnesium isotope compositions. Magnesium isotope ratios change as a result of silicate vapour loss, which preferentially contains the lighter isotopes. In this way, we estimated that more than 40 per cent of the Earth’s mass was lost during its construction. This cowboy building job, as one of my co-authors described it, was also responsible for creating the Earth’s unique composition.”

To break it down, accretion consists of clumps of material colliding with neighboring clumps to form larger objects. This process is very chaotic, and material is often lost as well as accumulated due to the extreme heat generated by these high-speed collisions. This heat is also believed to have created oceans of magma on the planets as they formed, not to mention temporary atmospheres of vaporized rock.

Until planets become about the same size as Mars, their force of gravitational attraction was too weak to hold onto these atmospheres. And as more collisions took place, the composition of these atmosphere and of the planets themselves would have changes substantially. How exactly the terrestrial planets – Mercury, Venus, Earth and Mars – obtained their current, volatile-poor compositions over time is what scientists have hoped to address.

Artist impression of the Late Heavy Bombardment period. Credit: NASA

For example, some believe that the planets current compositions are the result of particular combinations of gas and dust during the earliest periods of planet formation – where terrestrial planets are silicate/metal rich, but volatile poor, because of which elements were most abundant closest to the Sun. Others have suggested that their current composition is a consequence of their violent growth and collisions with other bodies.

To shed light on this, Dr. Hin and his associates analyzed samples of Earth, along with meteorites from Mars and the asteroid Vesta using a new analytical approach. This technique is capable of obtaining more accurate measurements of magnesium isotope rations than any previous method. This method also showed that all differentiated bodies – like Earth, Mars and Vesta – have isotopically heavier magnesium compositions than chondritic meteorites.

From this, they were able to draw three conclusions. For one, they found that Earth, Mars and Vesta have distinct magnesium isotope rations that could not be explained by condensation from the Solar Nebula. Second, they noted that the study of heavy magnesium isotopes revealed that in all cases, the planets lost about 40% percent of their mass during their formation period, following repeated episodes of vaporization.

Last, they determined that the accretion process results in other chemical changes that generate the unique chemical characteristics of Earth. In short, their study showed that Earth, Mars and Vesta all experiences significant losses of material after formation, which means that their peculiar compositions were likely the result of collisions over time. As Dr Hin added:

“Our work changes our views on how planets attain their physical and chemical characteristics. While it was previously known that building planets is a violent process and that the compositions of planets such as Earth are distinct, it was not clear that these features were linked. We now show that vapour loss during the high energy collisions of planetary accretion has a profound effect on a planet’s composition.”

Their study also indicated that this violent formation process could be characteristic of planets in general. These findings are not only significant when it comes to the formation of the Solar System, but of extra-solar planets as well. When it comes time to explore distant star systems, the distinctive compositions of their planets will tell us much about the conditions from which they formed, and how they came to be.

Further Reading: University of Bristol, Nature

Posted on by Ken Kremer

NASA’s OSIRIS-REx Captures Lovely Blue Marble during Gravity Assist Swing-by to Asteroid Bennu

A color composite image of Earth taken on Sept. 22, 2017 by the MapCam camera on NASA’s OSIRIS-REx spacecraft just hours after the spacecraft completed its Earth Gravity Assist at a range of approximately 106,000 miles (170,000 kilometers). Credit: NASA/Goddard/University of Arizona
A color composite image of Earth taken on Sept. 22, 2017 by the MapCam camera on NASA’s OSIRIS-REx spacecraft just hours after the spacecraft completed its Earth Gravity Assist at a range of approximately 106,000 miles (170,000 kilometers). Credit: NASA/Goddard/University of Arizona

KENNEDY SPACE CENTER, FL – NASA’s OSIRIS-REx asteroid mission captured a lovely ‘Blue Marble’ image of our Home Planet during last Fridays (Sept. 22) successful gravity assist swing-by sending the probe hurtling towards asteroid Bennu for a rendezvous next August on a round trip journey to snatch pristine soil samples.

The newly released color composite image of Earth was taken on Sept. 22 by the spacecrafts MapCam camera.

It was taken at a range of approximately 106,000 miles (170,000 kilometers), just a few hours after OSIRIS-REx completed its critical Earth Gravity Assist (EGA) maneuver.

“NASA’s asteroid sample return spacecraft successfully used Earth’s gravity on Friday, Sept. 22 to slingshot itself on a path toward the asteroid Bennu, for a rendezvous next August,” the agency confirmed after receiving the eagerly awaited telemetry.

OSIRIS-Rex, which stands for Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer, is NASA’s first ever asteroid sample return mission.

As it swung by Earth at 12:52 p.m. EDT on Sept. 22, OSIRIS-REx passed only 10,711 miles (17,237 km) above Antarctica, just south of Cape Horn, Chile.

The probe departed Earth by following a flight path that continued north over the Pacific Ocean and has already travelled 600 million miles (1 billion kilometers) since launching on Sept. 8, 2016.

OSIRIS-REx flight path over Earth’s surface during the Sept. 22, 2017 slingshot over Antarctica at 12:52 a.m. EDT targeting the probe to Asteroid Bennu in August 2018. Credits: NASA’s Goddard Space Flight Center/University of Arizona

The preplanned EGA maneuver provided the absolutely essential gravity assisted speed boost required for OSIRIS-Rex to gain enough velocity to complete its journey to the carbon rich asteroid Bennu and back.

The mission was only made possible by the slingshot which provided a velocity change to the spacecraft of 8,451 miles per hour (3.778 kilometers per second).

“The encounter with Earth is fundamental to our rendezvous with Bennu,” said Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement.

“The total velocity change from Earth’s gravity far exceeds the total fuel load of the OSIRIS-REx propulsion system, so we are really leveraging our Earth flyby to make a massive change to the OSIRIS-REx trajectory, specifically changing the tilt of the orbit to match Bennu.”

The spacecraft conducted a post flyby science campaign by collecting images and science observations of Earth and the Moon that began four hours after closest approach in order to test and calibrate its onboard suite of five science instruments and help prepare them for OSIRIS-REx’s arrival at Bennu in late 2018.

NASA’s OSIRIS-REx spacecraft OTES spectrometer captured these infrared spectral curves during Earth Gravity Assist on Sept. 22 2017, hours after the spacecraft’s closest approach. Credit: NASA/Goddard/University of Arizona/Arizona State University

The MapCam camera Blue Marble image is the first one to be released by NASA and the science team.

The image is centered on the Pacific Ocean and shows several familiar landmasses, including Australia in the lower left, and Baja California and the southwestern United States in the upper right.

“The dark vertical streaks at the top of the image are caused by short exposure times (less than three milliseconds),” said the team.

“Short exposure times are required for imaging an object as bright as Earth, but are not anticipated for an object as dark as the asteroid Bennu, which the camera was designed to image.”

The instrument will gather additional data and measurements scanning the Earth and the Moon for three more days over the next two weeks.

“The opportunity to collect science data over the next two weeks provides the OSIRIS-REx mission team with an excellent opportunity to practice for operations at Bennu,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson.

“During the Earth flyby, the science and operations teams are co-located, performing daily activities together as they will during the asteroid encounter.”

A United Launch Alliance Atlas V rocket lifts off from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx spacecraft on the first U.S. mission to sample an asteroid, retrieve at least two ounces of surface material and return it to Earth for study. Liftoff was at 7:05 p.m. EDT on September 8, 2016. Credit: Ken Kremer/kenkremer.com

The OSIRIS-Rex spacecraft originally departed Earth atop a United Launch Alliance Atlas V rocket under crystal clear skies on September 8, 2016 at 7:05 p.m. EDT from Space Launch Complex 41 at Cape Canaveral Air Force Station, Florida.

Everything with the launch and flyby went exactly according to plan for the daring mission boldly seeking to gather rocks and soil from carbon rich Bennu.

OSIRIS-Rex is equipped with an ingenious robotic arm named TAGSAM designed to collect at least a 60-gram (2.1-ounce) sample and bring it back to Earth in 2023 for study by scientists using the world’s most advanced research instruments.

View of science instrument suite and TAGSAM robotic sample return arm on NASA’s OSIRIS-REx asteroid sampling spacecraft inside the Payloads Hazardous Servicing Facility at NASA’s Kennedy Space Center. Probe is slated for Sep. 8, 2016 launch to asteroid Bennu from Cape Canaveral Air Force Station, FL. Credit: Ken Kremer/kenkremer.com

Watch for Ken’s continuing onsite NASA mission and launch reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
Ken Kremer

NASA’s OSIRIS-REx spacecraft OVIRS spectrometer captured this visible and infrared spectral curve, which shows the amount of sunlight reflected from the Earth, after the spacecraft’s Earth Gravity Assist on Sept. 22, 2017. Credit: NASA/Goddard/University of Arizona
Posted on by Nancy Atkinson

Can Astronauts See Stars From the Space Station?

Stars and the limb of Earth seen in the background of the International Space Station on July 29, 2017. Credit: NASA/Jack Fischer.

I’ve often been asked the question, “Can the astronauts on the Space Station see the stars?” Astronaut Jack Fischer provides an unequivocal answer of “yes!” with a recent post on Twitter of a timelapse he took from the ISS. Fischer captured the arc of the Milky Way in all its glory, saying it “paints the heavens in a thick coat of awesome-sauce!”

But, you might be saying, “how can this be? I thought the astronauts on the Moon couldn’t see any stars, so how can anyone see stars in space?”

John W. Young on the Moon during Apollo 16 mission. Charles M. Duke Jr. took this picture. The LM Orion is on the left. April 21, 1972. Credit: NASA

It is a common misconception that the Apollo astronauts didn’t see any stars. While stars don’t show up in the pictures from the Apollo missions, that’s because the camera exposures were set to allow for good images of the bright sunlit lunar surface, which included astronauts in bright white space suits and shiny spacecraft. Apollo astronauts reported they could see the brighter stars if they stood in the shadow of the Lunar Module, and also they saw stars while orbiting the far side of the Moon. Al Worden from Apollo 15 has said the sky was “awash with stars” in the view from the far side of the Moon that was not in daylight.

Just like stargazers on Earth need dark skies to see stars, so too when you’re in space.

The cool thing about being in the ISS is that astronauts experience nighttime 16 times a day (in 45 minute intervals) as they orbit the Earth every 90 minutes, and can have extremely dark skies when they are on the “dark” side of Earth. Here’s another recent picture from Fischer where stars can be seen:

For stars to show up in any image, its all about the exposure settings. For example, if you are outside (on Earth) on a dark night and can see thousands of stars, if you just take your camera or phone camera and snap a quick picture, you’ll just get a darkness. Earth-bound astrophotographers need long-exposure shots to capture the Milky Way. Same is true with ISS astronauts: if they take long-exposure shots, they can get stunning images like this one:

This long exposure image of the night sky over Earth was taken on August 9, 2015 by a member of the Expedition 44 crew on board the International Space Station. Credit: NASA.

This image, set to capture the bright solar arrays and the rather bright Earth (even though its in twilight) reveals no stars:

In this timelapse of Earth at night, a few stars show up, but again, the main goal here was to have the camera capture the Earth:

Universe Today’s Bob King has a good, detailed explanation of how astronauts on the ISS can see stars on his Astro Bob blog Astrophysicist . Brian Koberlein explains it on his blog, here.

You can check out all the images that NASA astronauts take from the ISS on the “Astronaut Photography of Earth” site, and almost all the ISS astronauts and cosmonauts have social media accounts where they post pictures. Jack Fischer, currently on board, tweets great images and videos frequently here.

Posted on by Nancy Atkinson

Satellite Images Show a Trillion Ton Iceberg Broke Off Antarctica

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image of the gigantic new iceberg on July 12, 2017. NASA Earth Observatory image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response.

For several months, scientists have been keeping an eye on a piece of Antarctica’s Larsen C ice shelf, waiting for the inevitable. And now it has happened.

Sometime between July 10 and July 12, 2017 a trillion ton iceberg split off, “changing the outline of the Antarctic Peninsula forever,” said one scientist.

The new iceberg is now called A68, and at 2,240 square miles (5,800 square km) it is one of the biggest ever recorded, about the size of Delaware in the US, or twice the size of Luxembourg.

A fissure on the ice shelf first appeared several years ago, but seemed relatively stable until January 2016, when it began to lengthen. In January 2017 alone, the crack grew by 20 km, reaching a total length of about 175 km.

Witnessed by the Copernicus Sentinel-1 mission on 12 July 2017, a large iceberg has broken off the Larsen-C ice shelf, one of the largest icebergs on record. Credit: Modified Copernicus Sentinel data (2017), processed by ESA.

The calving of the iceberg was confirmed by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite and was reported this morning by Project MIDAS, an Antarctic research project based in the UK.

The MODIS instrument on NASA’s Aqua satellite also confirmed the complete separation of the iceberg.

Larsen C is a floating platform of glacial ice on the east side of the Antarctic Peninsula, is the fourth largest ice shelf ringing Earth’s southernmost continent. With the break-off of this iceberg, the Larsen C shelf area has shrunk by approximately 10 percent.

Some scientists say the Larsen C rift and iceberg calving is not a warning of imminent sea level rise, and linking climate change to this specific event is complicated. Adrian Luckman, Professor of Glaciology and Remote Sensing from Swansea University wrote a detailed explanation of this for The Conversation.

The new iceberg would barely fit inside Wales. Credit: Adrian Luckman / MIDAS

David Vaughan, glaciologist and Director of Science at British Antarctic Survey (BAS), said, “Larsen C itself might be a result of climate change, but, in other ice shelves we see cracks forming, which we don’t believe have any connection to climate change. For instance on the Brunt Ice Shelf where BAS has its Halley Station, there those cracks are a very different kind which we don’t believe have any connection to climate change.”

While Vaughan said they see no obvious signal that climate warming is causing the whole of Antarctica to break up, he added that there is little doubt that climate change is causing ice shelves to disappear in some parts of Antarctica at the moment.

“Around the Antarctic Peninsula, where we saw several decades of warming through the latter half of the 20th century, we have seen these ice shelves collapsing and ice loss increasing,” he said. “There are other parts of the Antarctica that which are losing ice to the oceans but those are affected less by atmospheric warming and more by ocean change.

Scientists said the loss of such a large piece is of interest because ice shelves along the peninsula play an important role in ‘buttressing’ glaciers that feed ice seaward, effectively slowing their flow.

“The interesting thing is what happens next, how the remaining ice shelf responds,” said Kelly Brunt, a glaciologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland in College Park. “Will the ice shelf weaken? Or possibly collapse, like its neighbors Larsen A and B? Will the glaciers behind the ice shelf accelerate and have a direct contribution to sea level rise? Or is this just a normal calving event?”

The U.S. National Ice Center will monitor the trajectory of the new iceberg, but they don’t expect it to travel far very fast, and it shouldn’t cause any immediate problems for navigation of ships.

See additional imagery and animations from Goddard Space Flight Center.

Sources and additional reading:
ESA, British Antarctic Survey, NASA.

Posted on by Matt Williams

How Long is a Day on the Moon?

A photo of the full moon, taken from Apollo 11 on its way home to Earth, from about 18,520 km (10,000 nm) away. Credit: NASA
A photo of the full moon, taken from Apollo 11 on its way home to Earth, from about 18,520 km (10,000 nm) away. Credit: NASA

The Moon has been around since the earliest days of the Solar System. To human beings, there has never been a time when we couldn’t look up in the night sky and either see the Moon hanging there, or know that it would be back the very next night (i.e. a New Moon). And thanks to the development of modern astronomy and space exploration, our understanding of the Moon has grown immensely.

For instance, we know that the Moon formed early in Earth’s history, and that it may have played an important role in the development of life here on Earth. We’ve also learned that Moon is tidally-locked with Earth, which means that one side is constantly facing towards it. But how long is a day on the Moon? With one side facing the Earth and the other side facing out, what constitutes a single day on the lunar surface?

To break it down simply, a day on the Moon lasts as long as 29.5 Earth days. In other words, if you were standing on the surface of the Moon, it would take 29.5 days for the Sun to move all the way across the sky and return to its original position again. However, as with all bodies in the Solar System, distinguishing between different types of days (based on different types of periods) is necessary.

Orbit and Rotation:

Since ancient times, lunar calendars have been based on thirteen months of 28 days each, reflecting the lunar cycle. But as astronomers have discovered from centuries of studying the Moon’s behavior, the Moon’s orbital period (i.e. the time it takes for the Moon to complete a single orbit around the Earth) is actually the equivalent of about 27.3 Earth days – or 27 days 7 hours 43 minutes and 11.5 seconds, to be precise.

And while the Moon rotates on its own axis, the speed at which it rotates (aka. it’s sidereal rotation) is very slow. In fact, it takes the Moon the equivalent of 27.3 Earth days to complete a single rotation on its axis, the same amount of time it takes to complete a single orbit around Earth.  What this means is that the Moon is tidally-locked with Earth.

In other words, the Moon always points the same face towards the Earth, which is why human beings are so familiar with the “face” of the Moon, and refer to the side that faces away from us as the “the dark side”. Therefore, if you were standing on the surface of the Moon, you would always see the Earth in exactly the same position, while the stars and the Sun would continue to move around in the sky.

Sidereal vs. Synodic Day:

However, the Moon’s sidereal rotation is not where we get a the value of a single lunar day from. While it takes 27.3 days for it to orbit the Earth, we have to keep in mind that the Earth is also orbiting the Sun. The Earth returns to its same position in orbit every 365 days. So in order for the Sun to catch up to its same position in the sky from the perspective of the Moon, it has to turn a little more.

The extra 2.2 days is the time for the Moon to catch up in its rotation. And while the amount of time the Moon takes to complete one turn on its axis with respect to the stars is 27.3 days (a sidereal day), the amount of time it takes for the Sun to return to the same position in the sky is called a synodic day, and that’s what takes 29.5 days.

Ergo, a single day on the Moon, with respect to the Sun returning to the same position in the sky, is actually about as long as an average month here on Earth. So if people are planning on living there someday, and aren’t living in the permanently shadowed craters that exist in the southern and norther polar regions, that’s something they might have to get used to.

As with all the bodies of the Solar System, it all comes down to a matter of perspective. And if you’re living on the Moon, your perspective on what constitutes a day will be vastly different from that of a person who was born on Earth.

We have written many interesting articles about how long a day is on the planets of the Solar System. Here’s How Long is a Day on the Other Planets of the Solar System?, How Long is a Day on Mercury?, How Long is a Day on Venus?, How Long is a Day on the Earth?, How Long is a Day on Mars?, How Long is a Day on Jupiter?, How Long is a Day on Saturn?, How Long is a Day on Uranus?, How Long is a Day on Neptune?, and How Long is a Day on Pluto?

For more information, check out NASA’s Lunar and Planetary Science page. And here’s NASA’s Solar System Exploration Guide.

Astronomy Cast also has a good episode on the subject. Listen here: Episode 17: Where Did the Moon Come From?

Source:

Posted on by Matt Williams

How Does Mercury Compare to Earth?

Mercury and Earth, size comparison. Credit: NASA / APL (from MESSENGER)

Mercury was appropriately named after the Roman messenger of the Gods. This is owed to the fact that its apparent motion in the night sky was faster than that of any of the other planets. As astronomers learned more about this “messenger planet”, they came to understand that its motion was due to its close orbit to the Sun, which causes it to complete a single orbit every 88 days.

Mercury’s proximity to the Sun is merely one of its defining characteristics. Compared to the other planets of the Solar System, it experiences severe temperature variations, going from very hot to very cold. It’s also very rocky, and has no atmosphere to speak of. But to truly get a sense of how Mercury stacks up compared to the other planets of the Solar System, we need to a look at how Mercury compares to Earth.

Size, Mass and Orbit:

The diameter of Mercury is 4,879 km, which is approximately 38% the diameter of Earth. In other words, if you put three Mercurys side by side, they would be a little larger than the Earth from end to end. While this makes Mercury smaller than the largest natural satellites in our system – such as Ganymede and Titan – it is more massive and far more dense than they are.

Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Image Credit: NASA/JHUAPL/Carnegie Institution of Washington

In fact, Mercury’s mass is approximately 3.3 x 1023 kg (5.5% the mass of Earth) which means that its density – at 5.427 g/cm3 – is the second highest of any planet in the Solar System, only slightly less than Earth’s (5.515 g/cm3). This also means that Mercury’s surface gravity is 3.7 m/s2, which is the equivalent of 38% of Earth’s gravity (0.38 g). This means that if you weighed 100 kg (220 lbs) on Earth, you would weigh 38 kg (84 lbs) on Mercury.

Meanwhile, the surface area of Mercury is 75 million square kilometers, which is approximately 10% the surface area of Earth. If you could unwrap Mercury, it would be almost twice the area of Asia (44 million square km). And the volume of Mercury is 6.1 x 1010 km3, which works out to 5.4% the volume of Earth. In other words, you could fit Mercury inside Earth 18 times over and still have a bit of room to spare.

In terms of orbit, Mercury and Earth probably could not be more different. For one, Mercury has the most eccentric orbit of any planet in the Solar System (0.205), compared to Earth’s 0.0167. Because of this, its distance from the Sun varies between 46 million km (29 million mi) at its closest (perihelion) to 70 million km (43 million mi) at its farthest (aphelion).

This puts Mercury much closer to the Sun than Earth, which orbits at an average distance of 149,598,023 km (92,955,902 mi), or 1 AU. This distance ranges from 147,095,000 km (91,401,000 mi) to 152,100,000 km (94,500,000 mi) – 0.98 to 1.017 AU. And with an average orbital velocity of 47.362 km/s (29.429 mi/s), it takes Mercury a total 87.969 Earth days to complete a single orbit – compared to Earth’s 365.25 days.

The Orbit of Mercury during the year 2006. Credit: Wikipedia Commons/Eurocommuter

However, since Mercury also takes 58.646 days to complete a single rotation, it takes 176 Earth days for the Sun to return to the same place in the sky (aka. a solar day). So on Mercury, a single day is twice as long as a single year. Meanwhile on Earth, a single solar day is 24 hours long, owing to its rapid rotation of 1674.4 km/h. Mercury also has the lowest axial tilt of any planet in the Solar System – approximately 0.027°, compared to Earth’s 23.439°.

Structure and Composition:

Much like Earth, Mercury is a terrestrial planet, which means it is composed of silicate minerals and metals that are differentiated between a solid metal core and a silicate crust and mantle. For Mercury, the breakdown of these elements is higher than Earth. Whereas Earth is primarily composed of silicate minerals, Mercury is composed of 70% metallic and 30% of silicate materials.

Also like Earth, Mercury’s interior is believed to be composed of a molten iron that is surrounded by a mantle of silicate material. Mercury’s core, mantle and crust measure 1,800 km, 600 km, and 100-300 km thick, respectively; while Earth’s core, mantle and crust measure 3478 km, 2800 km, and up to 100 km thick, respectively.

What’s more, geologists estimate that Mercury’s core occupies about 42% of its volume (compared to Earth’s 17%) and the core has a higher iron content than that of any other major planet in the Solar System. Several theories have been proposed to explain this, the most widely accepted being that Mercury was once a larger planet that was struck by a planetesimal that stripped away much of the original crust and mantle.

Internal structure of Mercury: 1. Crust: 100–300 km thick 2. Mantle: 600 km thick 3. Core: 1,800 km radius. Credit: MASA/JPL

Surface Features:

In terms of its surface, Mercury is much more like the Moon than Earth. It has a dry landscape pockmarked by asteroid impact craters and ancient lava flows. Combined with extensive plains, these indicate that the planet has been geologically inactive for billions of years.

Names for these features come from a variety of sources. Craters are named for artists, musicians, painters, and authors; ridges are named for scientists; depressions are named after works of architecture; mountains are named for the word “hot” in different languages; planes are named for Mercury in various languages; escarpments are named for ships of scientific expeditions, and valleys are named after radio telescope facilities.

During and following its formation 4.6 billion years ago, Mercury was heavily bombarded by comets and asteroids, and perhaps again during the Late Heavy Bombardment period. Due to its lack of an atmosphere and precipitation, these craters remain intact billions of years later. Craters on Mercury range in diameter from small bowl-shaped cavities to multi-ringed impact basins hundreds of kilometers across.

The largest known crater is Caloris Basin, which measures 1,550 km (963 mi) in diameter. The impact that created it was so powerful that it caused lava eruptions on the other side of the planet and left a concentric ring over 2 km (1.24 mi) tall surrounding the impact crater. Overall, about 15 impact basins have been identified on those parts of Mercury that have been surveyed.

Enhanced-color image of Munch, Sander and Poe craters amid volcanic plains (orange) near Caloris Basin. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Earth’s surface, meanwhile, is significantly different. For starters, 70% of the surface is covered in oceans while the areas where the Earth’s crust rises above sea level forms the continents. Both above and below sea level, there are mountainous features, volcanoes, scarps (trenches), canyons, plateaus, and abyssal plains. The remaining portions of the surface are covered by mountains, deserts, plains, plateaus, and other landforms.

Mercury’s surface shows many signs of being geologically active in the past, mainly in the form of narrow ridges that extend up to hundreds of kilometers in length. It is believed that these were formed as Mercury’s core and mantle cooled and contracted at a time when the crust had already solidified. However, geological activity ceased billions of years ago and its crust has been solid ever since.

Meanwhile, Earth is still geologically active, owning to convection of the mantle. The lithosphere (the crust and upper layer of the mantle) is broken into pieces called tectonic plates. These plates move in relation to one another and interactions between them is what causes earthquakes, volcanic activity (such as the “Pacific Ring of Fire“), mountain-building, and oceanic trench formation.

Atmosphere and Temperature:

When it comes to their atmospheres, Earth and Mercury could not be more different. Earth has a dense atmosphere composed of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere. Earth’s atmosphere is also primarily composed of nitrogen (78%) and oxygen (21%) with trace concentrations of water vapor, carbon dioxide, and other gaseous molecules.

The Fast Imaging Plasma Spectrometer on board MESSENGER has found that the solar wind is able to bear down on Mercury enough to blast particles from its surface into its wispy atmosphere. Credit: Shannon Kohlitz, Media Academica, LLC

Because of this, the average surface temperature on Earth is approximately 14°C, with plenty of variation due to geographical region, elevation, and time of year. The hottest temperature ever recorded on Earth was 70.7°C (159°F) in the Lut Desert of Iran, while the coldest temperature was -89.2°C (-129°F) at the Soviet Vostok Station on the Antarctic Plateau.

Mercury, meanwhile, has a tenuous and variable exosphere that is made up of hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor, with a combined pressure level of about 10-14 bar (one-quadrillionth of Earth’s atmospheric pressure). It is believed this exosphere was formed from particles captured from the Sun, volcanic outgassing and debris kicked into orbit by micrometeorite impacts.

Because it lacks a viable atmosphere, Mercury has no way to retain the heat from the Sun. As a result of this and its high eccentricity, the planet experiences far more extreme variations in temperature than Earth does. Whereas the side that faces the Sun can reach temperatures of up to 700 K (427° C), the side that is in darkness can reach temperatures as low as 100 K (-173° C).

Despite these highs in temperature, the existence of water ice and even organic molecules has been confirmed on Mercury’s surface. The floors of deep craters at the poles are never exposed to direct sunlight, and temperatures there remain below the planetary average. In this respect, Mercury and Earth have something else in common, which is the presence of water ice in its polar regions.

Mercury’s Magnetic Field. Credit: NASA

Magnetic Fields:

Much like Earth, Mercury has a significant, and apparently global, magnetic field, one which is about 1.1% the strength of Earth’s. It is likely that this magnetic field is generated by a dynamo effect, in a manner similar to the magnetic field of Earth. This dynamo effect would result from the circulation of the planet’s iron-rich liquid core.

Mercury’s magnetic field is strong enough to deflect the solar wind around the planet, thus creating a magnetosphere. The planet’s magnetosphere, though small enough to fit within Earth, is strong enough to trap solar wind plasma, which contributes to the space weathering of the planet’s surface.

All told, Mercury and Earth are in stark contrast. While both are terrestrial in nature, Mercury is significantly smaller and less massive than Earth, though it has a similar density. Mercury’s composition is also much more metallic than that of Earth, and its 3:2 orbital resonance results in a single day being twice as long as a year.

But perhaps most stark of all are the extremes in temperature variations that Mercury goes through compared to Earth. Naturally, this is due to the fact that Mercury orbits much closer to the Sun than the Earth does and has no atmosphere to speak of. And its long days and long nights also mean that one side is constantly being baked by the Sun, or in freezing darkness.

We have written many stories about Mercury on Universe Today. Here’s Interesting Facts About Mercury, What Type of Planet is Mercury?, How Long is a Day on Mercury?, The Orbit of Mercury. How Long is a Year on Mercury?, What is the Surface Temperature of Mercury?, Water Ice and Organics Found at Mercury’s North Pole, Characteristics of Mercury,, Surface of Mercury, and Missions to Mercury

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Sources:

Posted on by Fraser Cain

Construction Tips from a Type 2 Engineer: Collaboration with Isaac Arthur

Type 2 Civ Tips!
Type 2 Civ Tips!

By popular request, Isaac Arthur and I have teamed up again to bring you a vision of the future of human space exploration. This time, we bring you practical construction tips from a pair of Type 2 Civilization engineers.

To make this collaboration even better, we’ve teamed up with two artists, Kevin Gill and Sergio Botero. They’re going to help create some special art, just for this episode, to help show what some of these megaprojects might look like.

Continue reading “Construction Tips from a Type 2 Engineer: Collaboration with Isaac Arthur”

Posted on by Fraser Cain

Can We Own Space? Buying Your Own Piece of the High Frontier

Space for Sale!
Space for Sale!


Compared to a regular human, the Earth is enormous. And compared to the Earth, the Universe is really enormous. Like, maybe infinitely enormous.

And yet, Earth is the only place humans are allowed to own. You can buy a plot of land in the city or the country, but you can’t buy land on the Moon, on Mars or on Alpha Centauri.

It’s not that someone wouldn’t be willing to sell it to you. I could point you at a few locations on the internet where someone would be glad to exchange your “Earth money” for some property rights on the Moon. But I can also point you to a series of United Nations resolutions which clearly states that outer space should be free for everyone. Not even the worst rocky outcrop of Maxwell Montes on Venus, or the bottom of Valles Marineris on Mars can be bought or sold.

However, the ability to own property is one of the drivers of the modern economy. Most people either own land, or want to own land. And if humans do finally become a space faring civilization, somebody is going to want to own the property rights to chunks of space. They’re going to want the mining rights to extract resources from asteroids and comets.

We’re going to want to know, once and for all, can I buy the Moon?

Until the space age, the question was purely hypothetical. It was like asking if you could own dragons, or secure the mining rights to dreams. Just in case those become possible, my vote to both is no.

The Sputnik spacecraft stunned the world when it was launched into orbit on Oct. 4th, 1954. Credit: NASA

But when the first satellite was placed into orbit in 1957, things became a lot less hypothetical. Once multiple nations had reached orbitable capabilities, it became clear that some rules needed to be figured out – the Outer Space Treaty.

The first version of the treaty was signed by the US, Soviet Union and the United Kingdom back in 1967. They were mostly concerned with preventing the militarization of space. You’re not allowed to put nuclear weapons into space, you’re not allowed to detonate nuclear weapons on other planets. Seriously, if you’ve got plans and they relate to nuclear weapons, just, don’t.

Can’t kill killer asteroids with nukes. Credit: Los Alamos National Lab

Over the years, almost the entire world has signed onto the Outer Space Treaty. 106 countries are parties and another 24 have signed on, but haven’t fully ratified it yet.

In addition to all those nuclear weapons rules, the United Nations agreed on several other rules. In fact, its full name is, The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies.

Here’s the relevant language:

Outer space, including the moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.

No country can own the Moon. No country can own Jupiter. No country can own a tiny planet, off in the corner of the Andromeda Galaxy. And no citizens or companies from those countries can own any property either.

And so far, no country has tried to. Seriously, space exploration is incredibly difficult. We’ve only set foot on the Moon a couple of times, decades ago, and never returned.

But with all the recent developments, it looks like we might be getting closer to wondering if we can own dragons, or a nice acreage on Mars.

Perhaps the most interesting recent development is the creation of not one, not two, but three companies dedicated to mining resources from asteroids: Planetary Resources, Kepler Energy, and Deep Space Industries.

Just a single small asteroid could contain many useful minerals, and there could potentially be tens of billions of dollars in profit for anyone who can sink robotic mining shafts into them.

Asteroid mining concept. Credit: NASA/Denise Watt

The three different companies have their own plans on how they’re going to identify potential mining targets and extract resources, and I’m not going to go into all the details of what it would take to mine an asteroid in this video.

But according to the Outer Space Treaty, is it legal? The answer, is: probably.

The original treaty was actually pretty vague. It said that no country can claim sovereignty over a world in space, but that doesn’t mean we can’t utilize some of its resources. In fact, future missions to the Moon and Mars depend on astronauts “living off the land”, harvesting local resources like ice to make air, drinking water and rocket fuel. Or building structures out of Martian regolith.

Mining an entire asteroid for sweet sweet profit is just a difference of scale.

In order to provide some clarity, the United States passed the U.S. Commercial Space Launch Competitiveness Act of 2015. This gave details on how space tourism should work, and described how companies might mine minerals from space. The gist of the law is, if an American citizen can get their hands on materials from an asteroid, they own it, and they’re free to sell it.

The Interplanetary Transport System blasting off. Credit: SpaceX

As you know, SpaceX is planning to colonize Mars. Well, so far, their plans include building the most powerful rocket ever built, and hurling human beings at Mars, hundreds at a time. The first mission is expected to blast off in 2024, so this is quickly becoming a practical issue.

What are the legalities of colonizing Mars? Will you own a chunk of land when you stumble out of the Interplanetary Transport Ship out on the surface of Mars?

Right now, you can imagine the surface of Mars like a research station on Antarctica. If SpaceX, an American company, builds a colony on Mars, then it’s essentially US government property. Anything that happens within that colony is under the laws of the United States.

If a group of colonists from China, for example, set out on their own, they would be building a little piece of China. And no matter what kind of facility they build, nobody within the team actually owns their homes.

If you’re out on the surface, away from a base, everything reverts to international law. Watch out for space pirates!

The space pirates were everywhere. Monday suddenly got a lot more interesting. Credit: NASA/JSC/Pat Rawlings, SAIC

Under the treaty, every facility is obliged to provide access to anyone else out there, which means that members of one facility are free to visit any other facility. You can’t lock your door and keep anyone out.

In fact, if anyone’s in trouble, you’re legally bound to do everything you can (within reason) to lend your assistance.

The bottom line is that the current Outer Space Treaty is not exactly prepared for the future reality of the colonization of Mars. As more and more people reach the Red Planet, you’d expect they’re going to want to govern themselves. We’ve seen this play out time and time again on Earth, so it won’t be surprising when the Mars colonies band together to declare their separation from Earth.

That said, as long as they’re reliant on regular supplies from Earth, they won’t be able to fully declare their independence. As long as they have interests on Earth, our planet’s governments will be able to squeeze them and maintain their dominance.

We've been dreaming about a Mars colony for a long time, as the lovely retro drawing shows. Will SpaceX finally give us one? Image: NASA
Credit: NASA

Once a Mars colony is fully self sufficient, though, which Elon Musk estimates will occur by 1 million inhabitants, Earth will have to recognize a fully independent Mars.

Space law is going to be one of the most interesting aspects of the future of space exploration. It’s really the next frontier. Concepts which were purely theoretical are becoming more and more concrete, and lawyers will finally be the heroes we always knew they could be.

If you’ve always wanted to be an astronaut, but your parents have always wanted you to be a lawyer, now’s your chance to do both. An astronaut space lawyer. I’m just saying, it’s an option.