What would it take to destroy our moon, and eliminate the enemy of stellar astronomy for all time?
In the immortal words of Mr. Burns, “ever since the beginning of time, man has wished to destroy the Sun.” Your days are numbered, Sun.
But supervillains, being the practical folks they are, know that a more worthy goal would be to destroy the Moon, or at least deface it horribly. Nothing wrecks a beautiful night sky like that hideous pockmarked spotlight. What would it take to destroy it and eliminate the enemy of stellar astronomy for all time?
Crack out your Acme brand blueprint paper and white pencils, it’s Wile E. Coyote time.
The energy it takes to dismantle a gravitationally held object is known as its binding energy, we talked about it in a Death Star episode and inventive ways to overcome it.
For example, the binding energy of the Earth is 2.2 x 10^32 joules. It’s a lot. The binding energy of a smaller object, like our Moon is a tidy little 1.2 x 10^29 joules. It takes about 1800 times more energy to destroy the Earth than it takes to destroy the Moon.
It’s 1800 times easier. That’s downright doable, isn’t it? That’s almost 2000 times easier. Which, on the scale of easy to less easy, is definitely closer to easy.
Take the event that created the Caloris Basin on Mercury. It’s a crater, 1,500 km across. Astronomers think that a big fat asteroid, a fatsteroid(?) around 100 km in diameter crashed into Mercury billions of years ago. This event released 1.3 x 10^26 joules of energy, carving out this giant pit. It’s a thousandth of the binding energy of the Moon. We’ll need something more.
Our Sun produces 3.8 x 10^26 joules of energy every second, the equivalent of about a billion hydrogen bombs. If you directed the full power of the Sun at the Moon for 15 minutes, it’d tear apart.
That’s quite a superweapon you’ve got there, perhaps you’ll want to mount that on a space station and take it for a cruise through a galaxy far far away?
If that scene took that long, we’d have fallen asleep. It’s as if millions of voices gradually became a little hoarse from crying out for a quarter of an hour. There’s another way you could tear the Moon apart that doesn’t require an astral gate accident: gravity.
Astronomers use the Roche Limit to calculate how close an object – like a moon – can orbit another object – like a planet.
This is the point where the difference between the tidal forces on the “front” and “backside” are large enough that the object is torn apart, and if this sounds familiar you might want to look up “spaghettification”.
Spaghettification. Credit: Streeter
This is all based on the radius of the planet and the density of the planet and moon. If the Moon got close enough to the Earth, around 18,000 km, it would pull apart and be shredded into a beautiful ring.
And then the objects in the ring would enter the Earth’s atmosphere and rain down beautiful destruction for thousands of years.
Fortunately or unfortunately, depending your position in this “Die Moon, Die” discussion, the Moon is drifting away from the Earth. It’ll never be closer than it is right now, at almost 400,000 km, without a little nudge.
Phobos, the largest moon orbiting Mars is slowly approaching the planet, and astronomers think it’ll reach the Roche Limit in the next few million years.
It turns out that if we really want to destroy the Moon, we’ll need to destroy all life on Earth as well.
Now we know your new supervillain project, what’s your supervillain name? Tell us your handle in the comments below.
How long would it take for the gravitational well created by the Sun to disappear, and the Earth and the rest of the planets fly off into space?
In the very first episode of the Guide to Space, a clean shaven version of me, hunched over in my basement explained how long it takes for light to get from the Sun to the Earth. To answer that question, it takes light about 8 minutes and 20 seconds to make the trip.
In other words, if the Sun suddenly disappeared from space itself, we’d still see it shining in the sky for over 8 minutes before the everything went dark. Martians would take about 12 minutes to notice the Sun was gone, and New Horizons which is nearly at Pluto wouldn’t see a change for over 4 hours.
Although this idea is a little mind-bending, I’m sure you’ve got your head wrapped around it. We’ve sure gone on about it here on this show. The further you look into space, the further you’re looking back in time because of the speed of light, but have you ever considered the speed of gravity?
Let’s go back to that original example and remove the Sun again. How long would it take for the gravitational well created by the Sun to disappear.
When would the Earth and the rest of the planets fly off into space without the Sun holding the whole Solar System together with its gravity? Would it happen instantly, or would it take time for the information to reach Earth?
It sounds like a simple question, but it’s actually really tough to tell. The force of gravity, compared to other forces in the Universe, is actually pretty weak. It’s practically impossible to test in the laboratory.
According to Einstein’s Theory of Relativity, distortions in spacetime caused by mass – also known as gravity – will propagate out at the speed of light. In other words, the light from the Sun and the gravity of the Sun should disappear at exactly the same time from the Earth’s perspective.
But that’s just a theory and a bunch of fancy math. Is there any way to test this out in reality? Astronomers have figured a way to deduce this indirectly by watching the interactions with massive objects in space.
In the binary system PSR 1913+16, there’s a pair of pulsars orbiting each other within just a few times bigger than the width of the Sun. As they spin around each other, the pulsars warp the spacetime themselves by releasing gravitational waves. And this release of gravitational waves causes the pulsars to slow down.
It’s amazing that astronomers can even measure this orbital decay, but the even more amazing part is that they use this process to measure the speed of gravity. When they did the calculations, astronomers determined the speed of gravity to be within 1% of the speed of light – that’s close enough.
Scientists have also used careful observations of Jupiter to get at this number. By watching how Jupiter’s gravity warps the light from a background quasar as it passes in front, they were able to determine that the speed of gravity is between 80% and 120% of the speed of light. Again, that’s close enough.
So there you go. The speed of gravity equals the speed of light. And should the Sun suddenly disappear, we’ll be glad to get all the bad news at the same time.
Gravity is a harsh mistress. Tell us a story about a time gravity was too fast for you. Put it in the comments below.
Every great adventure begins with a dream. Explorers look into the unknown and set a course for discovery. Many years ago, the US launched men off planet Earth and hurtled them to the Moon. The next great space milestone is certainly to put a human boot print on Mars. In this dream and adventure of exploration, women and men will not only walk on Mars, but inhabit it.
This aspiration of putting humans on Mars is not a new one. As a spacefaring nation, we could have reached there decades ago. In How We’ll Live on Mars, author Stephen L. Petranek examines how we’ll get to Mars within this century and discusses the opportunity for a potential settlement on the Red Planet.
Find out below how you can win a copy of this new book.
As a species it seems necessary and imminent for humans to exist off this singular planet we currently reside on. How will our journey to Mars happen? What are the pitfalls? And, most importantly, who is leading the charge?
Petranek discusses how private companies are filling a vacuum left by NASA’s mothballing of the Saturn V. NASA’s primary focus on the shuttle and then its retirement has left us currently unable to launch humans from US soil. Elon Musk and his Space Exploration Technologies Corp (SpaceX) are given proper attention in this book thanks to their accomplishments thus far and their push for further achievements including a goal of Mars. Other private companies and in fact, other nations, are setting their sights on sending rovers to and eventually occupying Mars.
Chapter 6 of this book is titled “Living on Mars.” Petranek aptly notes, “Humans need four things to survive on Earth – food, water, shelter, and clothing. Humans need five things to survive on Mars – food, water, shelter, clothing, and oxygen. The successful procurement of these five essential resources will secure humanity’s future as an interplanetary species.”
This presents a major hurdle. For example, an important goal is finding accessible water – a key ingredient for human survival. Making potable water on a planet far from home is not a simple task, but it is a possible one. The challenges for survival do not end there.
How We’ll Live on Mars, a TED Books original publication, is a quick and worthy read. Stephen L. Petranek’s writing style is fluid; the information is well presented and thoughtful. The first human footprint on Mars is fast approaching reality. As a species we will tune in to watch the broadcast – albeit one with a delay for the signal travel time – of a major milestone in history. This book gives a concise examination of where we’ve been, what we’re likely to see on the road to get there and what will happen once on Mars. I recommend adding this to your reading list.
Thanks to Simon & Schuster, Universe Today has three copies of this book to give away to our readers. The publisher has specified that for this contest, winners need to be from the US.
In order to be entered into the giveaway drawing, just put your email address into the box at the bottom of this post (where it says “Enter the Giveaway”) before Wednesday, July 15, 2015. We’ll send you a confirmation email, so you’ll need to click that to be entered into the drawing. If you’ve entered our giveaways before you should also receive an email with a link on how to enter.
Astronomer Copernicus, or Conversations with God, by Matejko. Credit: frombork.art.pl/pl/
When it comes to understanding our place in the universe, few scientists have had more of an impact than Nicolaus Copernicus. The creator of the Copernican Model of the universe (aka. heliocentrism), his discovery that the Earth and other planets revolved the Sun triggered an intellectual revolution that would have far-reaching consequences.
In addition to playing a major part in the Scientific Revolution of the 17th and 18th centuries, his ideas changed the way people looked at the heavens, the planets, and would have a profound influence over men like Johannes Kepler, Galileo Galilei, Sir Isaac Newton and many others. In short, the “Copernican Revolution” helped to usher in the era of modern science.
Copernicus’ Early Life:
Copernicus was born on February 19th, 1473 in the city of Torun (Thorn) in the Crown of the Kingdom of Poland. The youngest of four children to a well-to-do merchant family, Copernicus and his siblings were raised in the Catholic faith and had many strong ties to the Church.
His older brother Andreas would go on to become an Augustinian canon, while his sister, Barbara, became a Benedictine nun and (in her final years) the prioress of a convent. Only his sister Katharina ever married and had children, which Copernicus looked after until the day he died. Copernicus himself never married or had any children of his own.
Nicolaus Copernicus portrait from Town Hall in Torun (Thorn), 1580. Credit: frombork.art.pl
Born in a predominately Germanic city and province, Copernicus acquired fluency in both German and Polish at a young age, and would go on to learn Greek and Italian during the course of his education. Given that it was the language of academia in his time, as well as the Catholic Church and the Polish royal court, Copernicus also became fluent in Latin, which the majority of his surviving works are written in.
Copernicus’ Education:
In 1483, Copernicus’ father (whom he was named after) died, whereupon his maternal uncle, Lucas Watzenrode the Younger, began to oversee his education and career. Given the connections he maintained with Poland’s leading intellectual figures, Watzenrode would ensure that Copernicus had great deal of exposure to some of the intellectual figures of his time.
Although little information on his early childhood is available, Copernicus’ biographers believe that his uncle sent him to St. John’ School in Torun, where he himself had been a master. Later, it is believed that he attended the Cathedral School at Wloclawek (located 60 km south-east Torun on the Vistula River), which prepared pupils for entrance to the University of Krakow – Watzenrode’s own Alma mater.
In 1491, Copernicus began his studies in the Department of Arts at the University of Krakow. However, he quickly became fascinated by astronomy, thanks to his exposure to many contemporary philosophers who taught or were associated with the Krakow School of Mathematics and Astrology, which was in its heyday at the time.
A comparison of the geocentric and heliocentric models of the universe. Credit: history.ucsb.edu
Copernicus’ studies provided him with a thorough grounding in mathematical-astronomical knowledge, as well as the philosophy and natural-science writings of Aristotle, Euclid, and various humanist writers. It was while at Krakow that Copernicus began collecting a large library on astronomy, and where he began his analysis of the logical contradictions in the two most popular systems of astronomy.
These models – Aristotle’s theory of homocentric spheres, and Ptolemy’s mechanism of eccentrics and epicycles – were both geocentric in nature. Consistent with classical astronomy and physics, they espoused that the Earth was at the center of the universe, and that the Sun, the Moon, the other planets, and the stars all revolved around it.
Before earning a degree, Copernicus left Krakow (ca. 1495) to travel to the court of his uncle Watzenrode in Warmia, a province in northern Poland. Having been elevated to the position of Prince-Bishop of Warmia in 1489, his uncle sought to place Copernicus in the Warmia canonry. However, Copernicus’ installation was delayed, which prompted his uncle to send him and his brother to study in Italy to further their ecclesiastic careers.
In 1497, Copernicus arrived in Bologna and began studying at the Bologna University of Jurists’. While there, he studied canon law, but devoted himself primarily to the study of the humanities and astronomy. It was also while at Bologna that he met the famous astronomer Domenico Maria Novara da Ferrara and became his disciple and assistant.
An illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568. Credit: bnf.fr
Over time, Copernicus’ began to feel a growing sense of doubt towards the Aristotelian and Ptolemaic models of the universe. These included the problematic explanations arising from the inconsistent motion of the planets (i.e. retrograde motion, equants, deferents and epicycles), and the fact that Mars and Jupiter appeared to be larger in the night sky at certain times than at others.
Hoping to resolve this, Copernicus used his time at the university to study Greek and Latin authors (i.e. Pythagoras, Cicero, Pliny the Elder, Plutarch, Heraclides and Plato) as well as the fragments of historic information the university had on ancient astronomical, cosmological and calendar systems – which included other (predominantly Greek and Arab) heliocentric theories.
In 1501, Copernicus moved to Padua, ostensibly to study medicine as part of his ecclesiastical career. Just as he had done at Bologna, Copernicus carried out his appointed studies, but remained committed to his own astronomical research. Between 1501 and 1503, he continued to study ancient Greek texts; and it is believed that it was at this time that his ideas for a new system of astronomy – whereby the Earth itself moved – finally crystallized.
The Copernican Model (aka. Heliocentrism):
In 1503, having finally earned his doctorate in canon law, Copernicus returned to Warmia where he would spend the remaining 40 years of his life. By 1514, he began making his Commentariolus (“Little Commentary”) available for his friends to read. This forty-page manuscript described his ideas about the heliocentric hypothesis, which was based on seven general principles.
These seven principles stated that: Celestial bodies do not all revolve around a single point; the center of Earth is the center of the lunar sphere—the orbit of the moon around Earth; all the spheres rotate around the Sun, which is near the center of the Universe; the distance between Earth and the Sun is an insignificant fraction of the distance from Earth and Sun to the stars, so parallax is not observed in the stars; the stars are immovable – their apparent daily motion is caused by the daily rotation of Earth; Earth is moved in a sphere around the Sun, causing the apparent annual migration of the Sun; Earth has more than one motion; and Earth’s orbital motion around the Sun causes the seeming reverse in direction of the motions of the planets.
Andreas Cellarius’s illustration of the Copernican system, from the Harmonia Macrocosmica (1708). Credit: Public Domain
Thereafter he continued gathering data for a more detailed work, and by 1532, he had come close to completing the manuscript of his magnum opus – De revolutionibus orbium coelestium(On the Revolutions of the Heavenly Spheres). In it, he advanced his seven major arguments, but in more detailed form and with detailed computations to back them up.
However, due to fears that the publication of his theories would lead to condemnation from the church (as well as, perhaps, worries that his theory presented some scientific flaws) he withheld his research until a year before he died. It was only in 1542, when he was near death, that he sent his treatise to Nuremberg to be published.
Copernicus’ Death:
Towards the end of 1542, Copernicus suffered from a brain hemorrhage or stroke which left him paralyzed. On May 24th, 1543, he died at the age of 70 and was reportedly buried in the Frombork Cathedral in Frombork, Poland. It is said that on the day of his death, May 24th 1543 at the age of 70, he was presented with an advance copy of his book, which he smiled upon before passing away.
In 2005, an archaeological team conducted a scan of the floor of Frombork Cathedral, declaring that they had found Copernicus’ remains. Afterwards, a forensic expert from the Polish Police Central Forensic Laboratory used the unearthed skull to reconstruct a face that closely resembled Copernicus’ features. The expert also determined that the skull belonged to a man who had died around age 70 – Copernicus’ age at the time of his death.
These findings were backed up in 2008 when a comparative DNA analysis was made from both the remains and two hairs found in a book Copernicus was known to have owned (Calendarium Romanum Magnum, by Johannes Stoeffler). The DNA results were a match, proving that Copernicus’ body had indeed been found.
Copernicus’ 2010 grave in Frombork Cathedral, acknowledging him as a church canon and the father of heliocentricism. Credit: Wikipedia/Holger Weinandt
On May 22nd, 2010, Copernicus was given a second funeral in a Mass led by Józef Kowalczyk, the former papal nuncio to Poland and newly named Primate of Poland. Copernicus’ remains were reburied in the same spot in Frombork Cathedral, and a black granite tombstone (shown above) now identifies him as the founder of the heliocentric theory and also a church canon. The tombstone bears a representation of Copernicus’ model of the solar system – a golden sun encircled by six of the planets.
Copernicus’ Legacy:
Despite his fears about his arguments producing scorn and controversy, the publication of his theories resulted in only mild condemnation from religious authorities. Over time, many religious scholars tried to argue against his model, using a combination of Biblical canon, Aristotelian philosophy, Ptolemaic astronomy, and then-accepted notions of physics to discredit the idea that the Earth itself would be capable of motion.
However, within a few generation’s time, Copernicus’ theory became more widespread and accepted, and gained many influential defenders in the meantime. These included Galileo Galilei (1564-1642), who’s investigations of the heavens using the telescope allowed him to resolve what were seen at the time as flaws in the heliocentric model.
These included the relative changes in the appearances of Mars and Jupiter when they are in opposition vs. conjunction to the Earth. Whereas they appear larger to the naked eye than Copernicus’ model suggested they should, Galileo proved that this is an illusion caused by the behavior of light at a distance, and can be resolved with a telescope.
1973 Federal Republic of Germany 5-mark silver coin commemorating 500th anniversary of Copernicus’ birth. Credit: Wikipedia/Berlin-George
Through the use of the telescope, Galileo also discovered moons orbiting Jupiter, Sunspots, and the imperfections on the Moon’s surface, all of which helped to undermine the notion that the planets were perfect orbs, rather than planets similar to Earth. While Galileo’s advocacy of Copernicus’ theories resulted in his house arrest, others soon followed.
German mathematician and astronomer Johannes Kepler (1571-1630) also helped to refine the heliocentric model with his introduction of elliptical orbits. Prior to this, the heliocentric model still made use of circular orbits, which did not explain why planets orbited the Sun at different speeds at different times. By showing how the planet’s sped up while at certain points in their orbits, and slowed down in others, Kepler resolved this.
In addition, Copernicus’ theory about the Earth being capable of motion would go on to inspire a rethinking of the entire field of physics. Whereas previous ideas of motion depended on an outside force to instigate and maintain it (i.e. wind pushing a sail) Copernicus’ theories helped to inspire the concepts of gravity and inertia. These ideas would be articulated by Sir Isaac Newton, who’s Principia formed the basis of modern physics and astronomy.
Today, Copernicus is honored (along with Johannes Kepler) by the liturgical calendar of the Episcopal Church (USA) with a feast day on May 23rd. In 2009, the discoverers of chemical element 112 (which had previously been named ununbium) proposed that the International Union of Pure and Applied Chemistry rename it copernicum (Cn) – which they did in 2011.
Mosaic image of the Copernicus Crater on the Moon, taken by the Lunar Reconnaissance Orbiter, . Credit: NASA/LRO
In 1973, on the 500th anniversary of his birthday, the Federal Republic of Germany (aka. West Germany) issued a 5 Mark silver coin (shown above) that bore Copernicus’ name and a representation of the heliocentric universe on one side.
In August of 1972, the Copernicus– an Orbiting Astronomical Observatory created by NASA and the UK’s Science Research Council – was launched to conduct space-based observations. Originally designated OAO-3, the satellite was renamed in 1973 in time for the 500th anniversary of Copernicus’ birth. Operating until February of 1981, Copernicus proved to be the most successful of the OAO missions, providing extensive X-ray and ultraviolet information on stars and discovering several long-period pulsars.
Two craters, one located on the Moon, the other on Mars, are named in Copernicus’ honor. The European Commission and the European Space Agency (ESA) is currently conducting the Copernicus Program. Formerly known as Global Monitoring for Environment and Security (GMES), this program aims at achieving an autonomous, multi-level operational Earth observatory.
On February 19th, 2013, the world celebrated the 540th anniversary of Copernicus’ birthday. Even now, almost five and a half centuries later, he is considered one of the greatest astronomers and scientific minds that ever lived. In addition to revolutionizing the fields of physics, astronomy, and our very concept of the laws of motion, the tradition of modern science itself owes a great debt to this noble scholar who placed the truth above all else.
The terrestrial planets of our Solar System at approximately relative sizes. From left, Mercury, Venus, Earth and Mars. Credit: Lunar and Planetary Institute
In studying our Solar System over the course of many centuries, astronomers learned a great deal about the types of planets that exist in our universe. This knowledge has since expanded thanks to the discovery of extrasolar planets, many of which are similar to what we have observed here at home.
For example, while hundreds of gas giants of varying size have been detected (which are easier to detect because of their size), numerous planets have also been spotted that are similar to Earth – aka. “Earth-like”. These are what is known as terrestrial planets, a designation which says a lot about a planet how it came to be.
Definition:
Also known as a telluric or rocky planet, a terrestrial planet is a celestial body that is composed primarily of silicate rocks or metals and has a solid surface. This distinguishes them from gas giants, which are primarily composed of gases like hydrogen and helium, water, and some heavier elements in various states.
The term terrestrial planet is derived from the Latin “Terra” (i.e. Earth). Terrestrial planets are therefore those that are “Earth-like”, meaning they are similar in structure and composition to planet Earth.
Artist’s concept for the range of Earth-like extrasolar planets that have been discovered in recent years. Credit: NASA/JPL
Composition and Characteristics:
All terrestrial planets have approximately the same type of structure: a central metallic core composed of mostly iron, with a surrounding silicate mantle. Such planets have common surface features, which include canyons, craters, mountains, volcanoes, and other similar structures, depending on the presence of water and tectonic activity.
Terrestrial planets also have secondary atmospheres, which are generated through volcanism or comet impacts. This also differentiates them from gas giants, where the planetary atmospheres are primary and were captured directly from the original solar nebula.
Terrestrial planets are also known for having few or no moons. Venus and Mercury have no moons, while Earth has only the one (the Moon). Mars has two satellites, Phobos and Deimos, but these are more akin to large asteroids than actual moons. Unlike the gas giants, terrestrial planets also have no planetary ring systems.
The Earth’s interior structure, shown here as consisting of multiple “layers”. Credit: discovermagazine.com
Solar Terrestrial Planets:
All those planets found within the Inner Solar System – Mercury, Venus, Earth and Mars – are examples of terrestrial planets. Each are composed primarily of silicate rock and metal, which is differentiated between a dense, metallic core and a silicate mantle. The Moon is similar, but has a much smaller iron core.
Io and Europa are also satellites that have internal structures similar to that of terrestrial planets. In the case of the former, models of the moon’s composition suggest that the mantle is composed primarily of silicate rock and iron, which surrounds a core of iron and iron sulphide. Europa, on the other hand, is believed to have an iron core that is surrounded by an outer layer of water.
Dwarf planets, like Ceres and Pluto, and other large asteroids are similar to terrestrial planets in the fact that they do have a solid surface. However, they differ in that they are, on average, composed of more icy materials than rock.
Extrasolar Terrestrial Planets:
Most of the planets detected outside of the Solar System have been gas giants, owing to the fact that they are easier to spot. However, since 2005, hundreds of potentially terrestrial extrasolar planets have been found – mainly by the Kepler space mission. Most of these have been what is known as “super-Earths” (i.e. planets with masses between Earth’s and Neptune’s).
Examples of extrasolar terrestrial planets include Gliese 876 d, a planet that has a mass 7 to 9 times that of Earth. This planet orbits the red dwarf Gliese 876, which is located approximately 15 light years from Earth. The existence of three (or possibly four) terrestrial exoplanets was also confirmed between 2007 and 2010 in the Gliese 581 system, another red dwarf roughly 20 light years from Earth.
The smallest of these, Gliese 581 e, is only about 1.9 Earth masses, but orbits very close to the star. Two others, Gliese 581 c and Gliese 581 d, as well as a proposed fourth planet (Gliese 581 g) are more-massive super-Earths orbiting in or close to the habitable zone of the star. If true, this could mean that these worlds are potentially habitable Earth-like planets.
The first confirmed terrestrial exoplanet, Kepler-10b – a planet with between 3 and 4 Earth masses and located some 460 light years from Earth – was found in 2011 by the Kepler space mission. In that same year, the Kepler Space Observatory team released a list of 1235 extrasolar planet candidates, including six that were “Earth-size” or “super-Earth-size” (i.e. less than 2 Earth radii) and which were located within their stars’ habitable zones.
Since then, Kepler has discovered hundreds of planets ranging from Moon-sized to super-Earths, with many more candidates in this size range. As of January, 2013, 2740 planet candidates have been discovered.
Categories:
Scientists have proposed several categories for classifying terrestrial planets. Silicate planets are the standard type of terrestrial planet seen in the Solar System, which are composed primarily of a silicon-based rocky mantle and a metallic (iron) core.
Iron planets are a theoretical type of terrestrial planet that consists almost entirely of iron and therefore has a greater density and a smaller radius than other terrestrial planets of comparable mass. Planets of this type are believed to form in the high-temperature regions close to a star, and where the protoplanetary disk is rich in iron. Mercury is possible example, which formed close to our Sun and has a metallic core equal to 60–70% of its planetary mass.
Coreless planets are another theoretical type of terrestrial planet, one that consists of silicate rock but has no metallic core. In other words, coreless planets are the opposite of an iron planet. Coreless planets are believed to form farther from the star where volatile oxidizing material is more common. Though the Solar System has no coreless planets, chondrite asteroids and meteorites are common.
And then there are Carbon planets (aka. “diamond planets”), a theoretical class of planets that are composed of a metal core surrounded by primarily carbon-based minerals. Again, the Solar System has no planets that fit this description, but has an abundance of carbonaceous asteroids.
Until recently, everything scientists knew about planets – which included how they form and the different types that exist – came from studying our own Solar System. But with the explosion that has taken place in exoplanet discovery in the past decade, what we know about planets has grown significantly.
For one, we have come to understand that the size and scale of planets is greater than previously thought. What’s more, we’ve seen for the first time that many planets similar to Earth (which could also include being habitable) do in fact exist in other Solar Systems.
Who knows what we will find once we have the option of sending probes and manned missions to other terrestrial planets?
Astronomy Cast has episodes on the terrestrial planets including Mars, and an interview with Darin Ragozzine, one of the Kepler Space Mission scientists.
The symbols of the eight planets, and Pluto, Credit: insightastrology.net
In our long history of staring up at the stars, human beings have assigned various qualities, names, and symbols for all the objects they have found there. Determined to find patterns in the heavens that might shed light on life here on Earth, many of these designations also ascribed (and were based on) the observable behavior of the celestial bodies.
When it came to assigning signs to the planets, astrologists and astronomers – which were entwined disciplines in the past -made sure that these particular symbols were linked to the planets’ names or their history in some way.
Mercury:
This planet is named after the Roman god who was himself the messenger of the gods, noted for his speed and swiftness. The name was assigned to this body largely because it is the planet closest to the Sun, and which therefore has the fastest rotational period. Hence, the symbol is meant to represent Mercury’s helmet and caduceus – a herald’s staff with snakes and wings intertwined.
Mercury, as imaged by the MESSENGER spacecraft, which was named after the messenger of the gods because it has the fastest orbit around the Sun. Image Credit: NASA/JHU/Carnegie Institution.
Venus:
Venus’ symbol has more than one meaning. Not only is it the sign for “female”, but it also represents the goddess Venus’ hand mirror. This representation of femininity makes sense considering Venus was the goddess of love and beauty in the Roman Pantheon. The symbol is also the chemical sign for copper; since copper was used to make mirrors in ancient times.
Earth:
Earth’s sign also has a variety of meanings, although it does not refer to a mythological god. The most popular view is that the circle with a cross in the middle represents the four main compass points. It has also been interpreted as the Globus Cruciger, an old Christian symbol for Christ’s reign on Earth.
This symbol is not just limited to Christianity though, and has been used in various culture around the world. These include, but are not limited to, Norse mythology (where it appears as the Solar or Odin’s Cross), Native American cultures (where it typically represented the four spirits of direction and the four sacred elements), the Celtic Cross, the Greek Cross, and the Egyptian Ankh.
In fact, perhaps owing to the simplicity of the design, cross-shaped incisions have made appearances as petroglyphs in European cult caves dating all the way back to the beginning of the Upper Paleolithic, and throughout prehistory to the Iron Age.
Mars, as photographed with the Mars Global Surveyor, is identified with the Roman god of war. Credit: NASA
Mars:
Mars is named after the Roman god of war, owing perhaps to the planet’s reddish hue, which gives it the color of blood. For this reason, the symbol associated with Mars represents the god of wars’ shield and spear. Additionally, it is the same sign as the one used to represent “male”, and hence is associated with self-assertion, aggression, sexuality, energy, strength, ambition and impulsiveness.
Jupiter:
Jupiter’s sign, which looks like an ornate, oddly shaped “four,” also stands for a number of symbols. It has been said to represent an eagle, which was the Jovian god’s bird. Additionally, the symbol can stand for a “Z,” which is the first letter of Zeus – who was Jupiter’s Greek counterpart.
The line through the symbol is consistent with this, since it would indicate that it was an abbreviation for Zeus’ name. And last, but not least, there is the addition of the swirled line which is believed to represent a lighting bolt – which just happens to Jupiter’s (and Zeus’) weapon of choice.
Saturn:
Like Jupiter, Saturn resembles another recognizable character – this time, it’s an “h.” However, this symbol is actually supposed to represent Saturn’s scythe or sickle, because Saturn is named after the Roman god of agriculture (after the Greek god Cronus, leader of the Titans, who was also depicted as holding a scythe).
Jupiter, the largest planet in the Solar System, is appropriately named after the Roman father of the gods. Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Uranus:
The sign for Uranus is a combination of two other signs – Mars’ sign and the symbol of the Sun – because the planet is connected to these two in mythology. Uranus represented heaven in Roman mythology, and this ancient civilization believed that the Sun’s light and Mars’ power ruled the heavens.
Neptune:
Neptune’s sign is linked to the sea god Neptune, who the planet was named after. Appropriately, the symbol represents this planet is in the shape of the sea god’s trident.
Pluto:
Although Pluto was demoted to a dwarf planet in 2006, it still retains its old symbol. Pluto’s sign is a combination of a “P” and a “L,” which are the first two letters in Pluto as well as the initials of Percival Lowell, the astronomer who discovered the planet.
A full Moon flyby, as seen from Paris, France. Credit and copyright: Sebastien Lebrigand.
Moon:
The Moon is represented by a crescent shape, which is a clear allusion to how the Moon appears in the night sky more often than not. Since the Moon is also tied to people’s perceptions, moods, and emotional make-up, the symbol has also come to represents the mind’s receptivity.
Sun:
And then there’s the Sun, which is represented by a circle with a dot in the middle. In the case of the Sun, this symbol represents the divine spirit (circle) surrounding the seed of potential, which is a direct association with ancient Sun worship and the central role the Sun gods played in their respective ancient pantheons.
Examples of craters various craters on Mars. Credit: NASA/JPL/Univ. of Arizona.
We all know that Mars Needs Moms, but Dad rocks the Red Planet too! If you’re looking for a last-minute gift for Dad, the commercial space company Uwingu has a special Father’s Day promotion where you can name a crater on Mars after your dad (or any other special person in your life.) You’ll get a unique decorative Father’s Day certificate that you can download and print,or for an extra fee you can have the certificate professionally printed and framed.
Uwingu’s Mars Map Crater Naming Project at allows anyone to help name approximately 590,000 unnamed, scientifically cataloged craters on Mars. The company uses out-of-the-box idea to help address funding shortages for researchers, scientists, educators and students. Uwingu’s Mars map grandfathers in all the already named craters on Mars, but opens the remainder up for naming by people around the globe.
“This is an out-of-this-world way to honor dads across this planet,” said Dr. Alan Stern, Uwingu’s CEO. “Help your dad join our Dads on Mars club!”
Uwingu also announced that anyone purchasing the 50 largest craters named by Father’s Day will receive a 2-for-1 bonus: a gift certificate of equal value; allowing them to put additional crater names on the Mars map for free anytime in 2015.
Prices for naming craters depend on the size of the crater, and begin at $5. Half of Uwingu’s revenues go to fund the Uwingu Fund for space research and education grants.
As we’ve reported previously, Uwingu knows that the names likely won’t officially be approved by the IAU, but said they will be similar to the names given to features on Mars by the mission science teams (such as Mt. Sharp on Mars –the IAU-approved name is Aeolis Mons) or even like Pike’s Peak, a mountain in Colorado which was named by the public, in a way, as early settlers started calling it that, and it soon became the only name people recognized.
“Mars scientists and Apollo astronauts have named features on the Red Planet and the Moon without asking for the IAU’s permission,” Stern said. In the past, Stern has said that he realizes having people pay to suggest names for with no official standing may be controversial, and he’s willing to take the chance – and the heat – to try a innovative ways to provide funding in today’s climate of funding cuts.
Said Uwingu’s Ellen Butler, “I’m excited to name a crater on the Uwingu Mars map in honor of my own dad. It’ll be fun to share this with him on Father’s Day. I know he’ll love telling his friends that I named a crater for him!”
NASA's two small MarCO CubeSats will be flying past Mars in 2016 just as NASA's next Mars lander, InSight, is descending to land on the surface. MarCO, for Mars Cube One, will provide an experimental communications relay to inform Earth quickly about the landing. Credits: NASA/JPL-Caltech
NASA’s two small MarCO CubeSats will be flying past Mars in 2016 just as NASA’s next Mars lander, InSight, is descending to land on the surface. MarCO, for Mars Cube One, will provide an experimental communications relay to inform Earth quickly about the landing. Credits: NASA/JPL-Caltech See fly by and cubesat spacecraft graphics and photos below[/caption]
CubeSats are taking the next great leap for science – departing Earth and heading soon for the fourth rock from the Sun.
For the first time, two tiny CubeSat probes will launch into deep space in early 2016 on their first interplanetary expedition – aiming for the Red Planet as part of an experimental technology relay demonstration project aiding NASA’s next Mission to Mars; the InSight lander.
NASA announced the pair of briefcase-sized CubeSats, called Mars Cube One or MarCO, as a late and new addition to the InSight mission, that could substantially enhance communications options on future Mars missions. They were designed and built by NASA’s Jet Propulsion Laboratory (JPL), Pasadena, California.
InSight, which stands for Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport, is a stationary lander. It will join NASA’s surface science exploration fleet currently comprising of the Curiosity and Opportunity missions which by contrast are mobile rovers.
InSight is the first mission to understand the interior structure of the Red Planet. Its purpose is to elucidate the nature of the Martian core, measure heat flow and sense for “Marsquakes.”
The full-scale mock-up of NASA’s MarCO CubeSat held by Farah Alibay, a systems engineer for the technology demonstration, is dwarfed by the one-half-scale model of NASA’s Mars Reconnaissance Orbiter behind her. Credits: NASA/JPL-Caltech
Because of their small size – roughly 4 inches (10 centimeters) square) – and simplicity using off-the-shelf components, they are a favored platform for university students and others seeking low cost access to space – such as the Planetary Society’s recently successful Light Sail solar sailing cubesat demonstration launched in May. Six units are combined together to create MarCO.
Over the past few years many hundreds of cubesats have already been deployed in Earth orbit – including many dozens from the International Space Station(ISS) – but these will be the first going far beyond our Home Planet.
Data relayed by MarCO at 8 kbps in real time could reveal InSight’s fate on the Martian surface within minutes to mission controllers back on Earth, rather than waiting for a potentially prolonged period of agonizing nail-biting lasting an hour or more.
The two probes, known as MarCO-A and MarCO-B, will operate during InSight’s highly complex entry, descent and landing (EDL) operations as it descends through the thin Martian atmosphere. Their function is merely to quickly relay landing data. But the cubesats will have no impact on the ultimate success of the mission. They will intentionally sail by but not land on Mars.
“MarCO is an experimental capability that has been added to the InSight mission, but is not needed for mission success,” said Jim Green, director of NASA’s planetary science division at the agency’s headquarters in Washington, in a statement.
The MarCO Cubesats will serve as a test bed for a revolutionary communications mode that seeks to quickly relay data back to Earth about the status of InSight – in real time – as it plummets down to the Red Planet for the “Seven Minutes of Terror” that hopefully climaxes with a soft landing.
The MarCO duo will fly by past Mars at a planned distance and altitude of about 3,500 kilometers as InSight descends towards the surface during EDL operations. They will rapidly retransmit signals coming from the lander in real time, directly back to NASA’s huge Deep Space Network (DSN) receiving dish antennas back on Earth.
MarCO cubesats fly by trajectory for rapid communications relay as NASA’s InSight spacecraft lands on Mars in September 2016. Credit: NASA/JPL-Caltech
For this flight, six cubesats will be joined together to provide the additional capability required for the journey to Mars and to accomplish their communications task.
The six-unit MarCO CubeSat has a stowed size of about 14.4 inches (36.6 centimeters) by 9.5 inches (24.3 centimeters) by 4.6 inches (11.8 centimeters) and weighs 14 kilograms.
The solar powered probes will be outfitted with UHF and X-band communications gear as well as propulsion, guidance and more.
The overall cost to design, build, launch and operate MarCO-A and MarCO-B is approximately $13 million, a NASA spokesperson told Universe Today.
InSight and MarCO are slated to blastoff together on March 4, 2016 atop a United Launch Alliance Atlas V rocket from Vandenberg Air Force Base, California.
After launch, both MarCO CubeSats will separate from the Atlas V booster and travel along their own trajectories to the Red Planet.
“MarCO will fly independently to Mars,” says Green.
They will be navigated independently from InSight. They will all reach Mars at approximately the same time for InSight’s landing slated for Sept. 28, 2016.
MarCO’s two solar panels and two radio antennas will unfurl after being released from the Atlas booster. The high-gain, X-band antenna is a flat panel engineered to direct radio waves the way a parabolic dish antenna does,” according to a NASA description.
The softball-size radio “provides both UHF (receive only) and X-band (receive and transmit) functions capable of immediately relaying information received over UHF.”
MarCO cubesat graphic annotated to show dimensions, instruments, physical characteristics and capabilities. Credit: NASA/JPL-Caltech
During EDL, InSight will transmit landing data via UHF radio to the MarCO cubesats sailing past Mars as well as to NASA’s Mars Reconnaissance Orbiter (MRO) soaring overhead.
MarCO will assist InSight by receiving the lander information transmitted in the UHF radio band and then immediately forward EDL information to Earth using the X-band radio. By contrast, MRO cannot simultaneously receive information over one band while transmitting on another, thus delaying confirmation of a successful landing possibly by an hour or more.
Engineers for NASA’s MarCO technology demonstration display a full-scale mechanical mock-up of the small craft in development as part of NASA’s next mission to Mars. Mechanical engineer Joel Steinkraus and systems engineer Farah Alibay are on the team at NASA’s Jet Propulsion Laboratory, Pasadena, California, preparing twin MarCO (Mars Cube One) CubeSats for a March 2016 launch. Credit: NASA/JPL-Caltech
“Ultimately, if the MarCO demonstration mission succeeds, it could allow for a “bring-your-own” communications relay option for use by future Mars missions in the critical few minutes between Martian atmospheric entry and touchdown,” say NASA officials.
It’s also very beneficial and critical to the success of future missions to have a stream of data following the progress of past missions so that lessons can be learned and applied, whatever the outcome.
“By verifying CubeSats are a viable technology for interplanetary missions, and feasible on a short development timeline, this technology demonstration could lead to many other applications to explore and study our solar system,” says NASA.
InSight will smash into the Martian atmosphere at high speeds of approximately 13,000 mph in September 2016 and then decelerate within a few minutes for landing via a heat shield, retro rocket and parachute assisted touchdown on the plains at flat-lying terrain at “Elysium Planitia,” some four degrees north of Mars’ equator, and a bit north of the Curiosity rover.
As I reported in recently here, InSight has now been assembled into its flight configuration and begun a comprehensive series of rigorous environmental stress tests that will pave the path to launch in 2016 on a mission to unlock the riddles of the Martian core.
The countdown clock is ticking relentlessly towards liftoff in less than nine months time in March 2016.
NASA’s InSight Mars lander spacecraft in a Lockheed Martin clean room near Denver. As part of a series of deployment tests, the spacecraft was commanded to deploy its solar arrays in the clean room to test and verify the exact process that it will use on the surface of Mars. Credits: NASA/JPL-Caltech/Lockheed Martin
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Spectacular 3D view of Arsia Mons, a huge volcano on Mars, taken by camera on India's Mars Orbiter Mission (MOM). Credit: ISRO
Spectacular 3D view of Arsia Mons, a huge volcano on Mars, taken by camera on India’s Mars Orbiter Mission (MOM). Credit: ISRO
Story updated with more details and imagery[/caption]
The Indian Space Research Organization (ISRO), India’s space agency, has recently published a beautiful gallery of images featuring a variety of picturesque Martian canyons, volcanoes, craters, moons and more.
We’ve gathered a collection here of MOM’s newest imagery snapped by the probes Mars Color Camera (MCC) for the enjoyment of Martian fans worldwide.
The spectacular 3D view of the Arsia Mons volcano, shown above, was “created by draping the MCC image on topography of the region derived from the Mars Orbiter Laser Altimeter (MOLA), one of five instruments on board NASA’s Mars Global Surveyor (MGS) spacecraft.
The Arsia Mons image was taken from Mars orbit on 1 April 2015 at a spatial resolution of 556 meters from an altitude of 10707 km. Volcanic deposits can be seen located at the flanks of the Mons, according to ISRO.
The view of Pital crater below was released in late May and taken on 23 April 2015. Pital is a 40 km wide impact crater located in the Ophir Planum region of Mars and the image shows a chain of small impact craters. It is located in the eastern part of Valles Marineris region, says an ISRO description. MCC took the image from an altitude of 808 km.
Pital crater is an impact crater located in Ophir Planum region of Mars, which is located in the eastern part of Valles Marineris region. This image is taken by Mars Color Camera (MCC) on 23-04-2015 at a spatial resolution of ~42 m from an altitude of 808 km. Credit: ISRO
It is an odd shaped crater, neither circular nor elliptical in shape, possibly due to “regional fracture in the W-E trending fracture zone.”
A trio of images, including one in stunning 3D, shows various portions of Valles Marineris, the largest known canyon in the Solar System.
Three dimensional view of Valles Marineris center portion from India’s MOM Mars Mission. Credit: ISRO
Valles Marineris stretches over 4,000 km (2,500 mi) across the Red Planet , is as much as 600 km wide and measures as much as 7 kilometers (4 mi) deep.
Valles Marineris from India’s Mars Mission. Credit: ISRO
For context here’s a previously taken global image of the red planet from MOM showing Valles Marinaris and Arsia Mons, which belongs to the Tharsis Bulge trio of shield volcanoes. They are both near the Martian equator.
Olympus Mons, Tharsis Bulge trio of volcanoes and Valles Marineris from ISRO’s Mars Orbiter Mission. Note the clouds and south polar ice cap. Credit: ISRO
Valles Marineris is often called the “Grand Canyon of Mars.” It spans about as wide as the entire United States.
A gorgeous view of Phobos, the largest of Mars’ two tiny moons, silhouetted against the surface is shown below.
Phobos, one of the two natural satellites of Mars silhouetted against the Martian surface. Credit: ISRO
MOM’s goal is to study Mars atmosphere, surface environments, morphology, and mineralogy with a 15 kg (33 lb) suite of five indigenously built science instruments. It is also sniffing for methane, a potential marker for biological activity.
MOM is India’s first deep space voyager to explore beyond the confines of her home planets influence and successfully arrived at the Red Planet after the “history creating” orbital insertion maneuver on Sept. 23/24, 2014 following a ten month journey from Earth. MOM swoops around Mars in a highly elliptical orbit whose nearest point to the planet (periapsis) is at about 421 km and farthest point (apoapsis) at about 76,000 km, according to ISRO.
It takes MOM about 3.2 Earth days or 72 hours to orbit the Red Planet.
Higher resolution view of a portion of Valles Marineris canyon from India’s MOM Mars Mission. Credit: ISRO
MOM was launched on Nov. 5, 2013 from India’s spaceport at the Satish Dhawan Space Centre, Sriharikota, atop the nations indigenous four stage Polar Satellite Launch Vehicle (PSLV) which placed the probe into its initial Earth parking orbit.
The $73 million MOM mission was expected to last at least six months. In March, ISRO extended the mission duration for another six months since its healthy, the five science instruments are operating fine and it has sufficient fuel reserves.
And with a communications blackout between Mars and Earth imminent as a result of natures solar conjunction, it’s the perfect time to catch up on all things Martian.
Solar conjunctions occur periodically between Mars and Earth about every 26 months, when the two planets line up basically in a straight line geometry with the sun in between as the two planets travel in their sun-centered orbits.
Since Mars will be located behind the Sun for most of June, communications with all the Terran spacecraft at the planet is diminished to nonexistent.
“MOM faces a communication outage during June 8-25,” according to The Hindu.
Normal science operations resume thereafter.
“Fuel on the spacecraft is not an issue,” ISRO Satellite Centre Director M. Annadurai told The Hindu.
Image of Tyrrhenus Mons in Hesperia Planum region taken by Mars Color Camera (MCC) on 25-02-2015 at a spatial resolution of 166m from an altitude of 3192km. Tyrrhenus Mons is an ancient martian volcano and image shows its timeworn gullies and wind streaks. Credit: ISRO
Including MOM, Earth’s invasion fleet at the Red Planet numbers a total of seven spacecraft comprising five orbiters from NASA, ESA and ISRO as well as the sister pair of mobile surface rovers from NASA – Curiosity and Opportunity.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
