Hubble Thirtieth Anniversary

Hubble's Thirtieth Anniversary

Lake Michigan seen from the International Space Station on a uncommonly clear day.
Canada is toward the bottom of the image. Image Credit: NASA

The Earth is a pretty cool place to live. It’s got tons of fresh air, drinkable water, awesome trees, and a whole bunch of people to hang out with.

Dramatic storm clouds on the edge of typhoon at sunset as seen from the International Space Station.
Basically imposssible to do astronomy through. Image Credit: NASA

The Earth kinda stinks if you’re an astronomer. It’s got tons of air above you that bounces light all around, water that just appears from thin air to cloud up the whole place, trees that don’t care one bit if they’re in your way, and there’s all these people everywhere who want to light the whole place up when it gets dark out. It’s really kind of a crummy place to set up a telescope.

Observatory telescopes at Mauna Kea, Hawaii.
Image Credit: Public Domain

But what are you going to do? You’re stuck here, for now. So diligent astronomer that you are, you haul your telescope away from all those people and trees. You carry it up the side of a mountain, so high up you need to bring extra oxygen just to breath, and up above the clouds. And yet, still there’s so much air still above you, rarified as it is, that it still bounces your image around. There’s just no escape from all that air.

And then there’s the planes. And the satellites. And then you look at your phone and some billionaire is planning to put… 12,000 more satellites up there?! Maybe 30,000 more after that?!

Being stuck on the Earth as an astronomer is a real downer. Where you’d really like to be is up there, up above all of that air and water and billionaires with their tens of thousands of satellites. If you could put your telescope up there, it wouldn’t have to worry about the light of the image being bounced around. It would be able to see those wavelengths of light that get absorbed by the air. You could do real science that you just can’t do from the surface.

That’s the dream of the space-based telescope. An instrument immune to the obstacles of the Earth-based observing, and open up the ultraviolet and infrared universe to scientific exploration. It’s a dream that astronomers held since the earliest days of rocketry. Many telescopes have since been launched into space, and each of them has expanded the frontier of human understanding in exciting and unique ways. None has been as successful, famous, or iconic as the Hubble Space Telescope.

The Hubble Space Telescope is held in position above the service bay of
the space shuttle Endeavour by the shuttle's robotic arm. Image Credit: NASA

The Hubble Space Telescope launched in April 24, 1990 aboard the space shuttle Discovery. The telescope sports a 2.4 meter primary mirror, and the entire telescope is slightly larger a school bus. Because Hubble orbits above the atmosphere, it’s equipped with sensors that can see into the ultraviolet and infrared spectrums, light which would be absorbed by air and invisible to the eye.

The Pillars of Creation in the Eagle Nebula. The pillars
are immense columns of dust being compressed and forming new stars.
Image Credit: NASA, ESA/Hubble and the Hubble Heritage Team

Beyond the gorgeous images Hubble returned over the last 30 years, the telescope is infamously known for being blurry. After deployment, engineers discovered that Hubble’s primary mirror was ground to the wrong shape. The telescope became a punchline, and NASA feared it might be labeled a gigantic boondoggle. And who can blame them? The idea that the brightest minds at NASA made the mirror the wrong shape is inherently funny. What most people joking about it don’t realize is that the shape of the mirror was too flat at the edges by about 2,200 nanometers, or about one hundredth the thickness of a human hair. It might have been the wrong shape, but it was the most precisely machined mirror in history.

The precision eventually allowed Hubble to be repaired. Because the defect in the mirror was so well known and characterized, scientists developed sophisticated techniques to compensate for the error, and still produce usable images. They also designed corrective optics, new mirrors that would interrupt the light path to the instruments that could also compensate for the flaw. Essentially, these would be like glasses for the enormous telescope. The corrective optics were installed in Hubble in 1993 on the first space shuttle mission to service the telescope in orbit.

The Hubble Ultra Deep Field. The image contains nearly 10,000 galaxies
in an area of the sky the size of a tennis ball held 100 yards away.
Image Credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team.

This is itself worthy of note, because the Hubble Telescope was designed to be serviced by the space shuttle. Ultimately, astronauts worked on the telescope five times before the shuttle was retired in 2011. Each mission worked to increase and improve the capabilities of the telescope, furthering our understanding of the universe.

Over the last 30 years, Hubble has contributed immensely to our scientific knowledge. Some of the important discoveries that Hubble produced include:

• Constraining the age of the universe to 13.7 billion years
• Constraining the rate of expansion of the universe, including the discovery of dark energy
• The discovery of additional moons around Pluto
• Determining the mass and size of the Milky Way galaxy
• Discovery of the connection between galaxies and supermassive black holes
• Observing protoplanetary disks around stars forming in the Orion Nebula

Hubble is still working well today, but the writing is on the wall for the great space telescope. Like all near Earth satellites, Hubble is subject to drag forces from the incredibly thin outer edge of the Earth’s atmosphere. Originally this wouldn’t be an issue. During each of the space shuttle servicing missions, Hubble’s orbit was boosted using the shuttle’s rocket engines, counteracting the effects of atmospheric drag. But the space shuttle was retired in 2011, and there are no other vehicles capable of boosting Hubble in service today.

Moreover, no spacecraft today could ferry astronauts to service the telescope. Keeping the telescope pointing precisely and steady is obviously important for taking images of faint and distant objects. Hubble uses a set of high performance gyroscopes to maintain its pointing. These gyroscopes fail over time, and can no longer be replaced, meaning at some point Hubble may not be able to maintain pointing at its imaging targets. This would render the telescope unable to do science.

The Hubble Space Telescope above the limb of the Earth.
Image Credit: NASA

Eventually, whether or not the gyroscopes fail, Hubble will return to Earth. NASA estimates that the Hubble Space Telescope will reenter the Earth’s atmosphere and burn up some time between 2028 and 2040. When this happens, it’s likely that portions of the telescope, including parts of the mirror, will survive to the surface. A spectacular end to such an intrepid tool of discovery.

Test engineers stand infront of the James Webb
Space Telescope primary mirror.
Image Credit: NASA/Goddard/Chris Gunn

Successors to Hubble are already in progress. NASA’s next great space observatory, the James Webb Space Telescope, will have more than 5 times the light gathering area than the Hubble. It will be able to see further and fainter than Hubble ever could. Webb will orbit the L2 Earth-Sun Lagrange point, a point in space about 1.5 million kilometers from the Earth where the gravity from the Earth and Sun balance against the centrifugal force experienced on an object orbiting the Sun. This will be so far away that servicing it will be out of the question. But it will also be so far away it will be free from the influence of Earth’s atmosphere and should be able to operate for a very long time. The James Webb Space Telescope is scheduled to launch in 2021, but the project has been plagued with delays and could be pushed back further.

In the meantime, we’ll continue to use the Hubble Space Telescope to probe the depth of the universe and expand the frontier of human knowledge.

Consider Again That Dot

Consider Again That Dot

Portrait of Voyager 1 spacecraft in space. Image Credit: NASA/JPL-Caltech

Launched in September of 1977, Voyager 1 took advantage of a rare alignment of the outer planets of the solar system. Voyager 1’s mission has three major sections. The first was the exploration of Jupiter and Saturn. Next, and currently ongoing, is the exploration of the edge of solar system. Finally, once Voyager runs out of energy and falls silent, it will serve as a silent testament to a race of beings that sent their hopes to the stars.

Following Voyager 1’s close encounter with Saturn November 12, 1980, the planet’s gravity bent Voyager’s trajectory out of the plane of the solar system. It was now the fastest object ever built by humans, and it was on its way to exit the solar system. Voyager was already wildly successful. It had sent back incredible close up pictures of the gas giants Jupiter and Saturn.

The swirling maelstrom of the Great Red Spot.

This is the closest picture of the Great Red Spot taken by Voyager.
Image Credit: NASA / JPL-Caltech / Björn Jónsson CC BY-NC-SA 3.0

The majesty of the fine rings around Saturn.

This image of Saturn and its rings was captured as Voyager departed Saturn following its encounter.
Image Credit: NASA / JPL / color composite by Gordan Ugarkovic CC BY-NC-SA 3.0

It shed light on the moons of these planets, now worlds themselves, and discovered the great variety of moons in our backyard.

Io, a world dotted with huge, active volcanos.

The surface of Io, mottled yellow and white, and spotted with volcanos.
Image Credit: NASA / JPL / Ted Stryk CC BY-NC-SA 3.0

Europa, covered in a thick sheet of ice above an ocean of liquid water.

Europa's surface in half phase, crisscrossed by deep fissures in the ice.
Image Credit: NASA / JPL / Björn Jónsson CC BY-NC-SA 3.0

Titan, cloaked in a hazy, orange atmosphere; the only moon in the solar system to have one.

Titan's surface remains hidden beneath a smooth, orange atmosphere.
Image Credit: NASA / JPL / Gordan Ugarkovic CC BY-NC-SA 3.0

It cannot be overstated just how much the Voyager program contributed to our understanding of the planets. Even today, scientists examine the mountains of data sent back from Voyager, and are still making new discoveries.

There would be no further planets for Voyager 1 after Saturn. At some point, it would not make sense to continue powering its cameras. Nothing in Voyager’s field of view would appear as anything larger than a dot, and the electricity could be better used powering its other detectors, and sending those signals back to scientists on Earth.

Before the cameras were turned off, a group of scientists led by Carl Sagan campaigned for Voyager 1 to turn back and collect a series of images capturing the planets of the solar system one last time. There would be absolutely no science to learn in this Family Portrait; it would be purely sentimental. Sagan’s point of view prevailed over the resistance of others within NASA. On February 14, 1990, Voyager 1 took one last picture of home before it left forever.

Family Portrait of the planets of the solar system taken by Voyager 1. The planet locations are marked in the panorama by the first letter of their names, and an inset shows the detail of each.
Image Credit: NASA / JPL

The image of Earth received the name “Pale Blue Dot” because of the rhetoric used by Carl Sagan in his efforts to describe the subject of the picture. No description of the picture comes close to fully capturing the importance of the photograph besides Sagan’s. The two are forever intertwined. To quote Sagan from his book “Pale Blue Dot”:

The Pale Blue Dot. Earth is roughly in the center of the rightmost sunbeam.
Image Credit: NASA/JPL

Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.

At the time of capture, Voyager 1 was approximately 6 billion kilometers from Earth, more than 40 times the distance from Earth to the Sun. It is the most distant picture of Earth ever taken. NASA estimates that Earth occupies 0.12 pixels of the image. It is easy to misidentify Earth as noise. The light beams are reflections of the Sun occurring within the camera. The picture shows Earth as it is: a delicate point of light in the vast cosmic darkness and lit by a sunbeam.

The Voyager program is one of the grand scientific triumphs of human history. It is the initial reconnaissance of our solar system. It continues to contribute to science even today as the twin Voyager spacecraft enter interstellar space. But this image of the Earth, more than any other single image taken in the Voyager program, is the true gift of Voyager.

At 7pm on February 7, 2020, the Delta College Planetarium will be holding a special event commemorating the thirtieth anniversary of the capturing of the Pale Blue Dot, the end of the first phase of the Voyager missions. We will cover the history of the Voyager missions, and examine how Voyager changed our understanding of the planets.

Transit of Mercury 2019

The Transit of Mercury 2019

Are you ready for the Great Mercury Eclipse of 2019?

Mercury passing in front of the Sun May 9, 2016. Image Credit: Solar Dynamics Observatory, NASA

Ok, so it’s not exactly an eclipse, like the solar eclipse that passed over the United States in 2017, but it’s still pretty cool. On November 11, 2019, the planet Mercury will transit the Sun.

“Transit” is the technical name for eclipses; an eclipse is a special form of a transit. Transits occur when a smaller object passes directly in front of a larger astronomical object from your perspective. For example, a transit can happen when an asteroid passes in front of the Sun, or when the space station passes in front of the Moon. (The opposite of this, when a large object passes in front of a smaller one, is called an “occultation”. Frequently the Moon will pass in front of a planet, or an asteroid passes in front of a distant star blocking its light. These are common examples occultations.)

The planets of our solar system all orbit the Sun in nearly the same plane. You can think of them as moving around on an enormous tabletop with the Sun at the center. Two planets orbit the Sun inside the orbit of Earth, and that means that from time to time Mercury and Venus will pass directly between Earth and the Sun. Because the planets are “nearly” in the same plane and not “exactly” in the same plane, these transits occur relatively rarely, only when the geometry of the planets lines up just right.

Venus transiting the Sun on June 5, 2012. Venus appears as a
large black dot in the upper right. Sunspots are visible towards
the center of the Sun's disk. Image Credit: Brian Kennedy

Venus is by far the more impressive of the two transits, blocking enough sunlight to be visible to the naked eye (but you should never look directly at the Sun, because that can quickly damage your eyes permanently). Venus transits are also far rarer of the two. Venus transits occur in a strange pattern which repeats every 243 years. The first transit will occur followed by a second one 8 years later. Then 121 years will pass before the third, with the fourth following 8 years after that. Finally, another 105 years will pass before the pattern repeats. The last Venus transit occurred in 2012, and the next one won’t occur until 2117, so it is unlikely that anyone living today will see another in their lifetime.

Transits of Mercury are the next best thing. Mercury transits the Sun far more frequently than Venus, with transits occurring about 13 or 14 times in a century. This means that most people will have a chance at seeing one. The next transit of Mercury occurs on November 11, 2019. The following transit will occur in 2032, so this is the last chance for a while.

Mercury transiting the Sun on May 9, 2016. Mercury appears as
a small black dot in the lower right. Sunspots are visible toward
the center of the solar disk. Image Credit: Brian Kennedy

Mercury is far smaller and further away from Earth than Venus is, so it blocks much less of the Sun. Transits take many hours. The November 11 transit will last from about 7:35 am EST until about 1:04 pm EST. Throughout this time, Mercury will appear in silhouette, a small black dot against the surface of the Sun.

Of particular interest will be the times when Mercury enters and exits the disk of the Sun. During this time, a phenomenon called the “black drop” effect might be seen, when Mercury could appear less like a perfect circle, and more like an inky droplet. This effect is believed to be more pronounced with Venus, and is not well understood. The leading hypothesis is that the black drop effect is an optical effect that occurs because of some of the surface properties of the Sun. Recent observers of planetary transits have reported less pronounced or entirely absent black drop effects. This may have something to do with the superior telescopes that are widely available today.

Mercury exiting the Sun at the end of the 2016 transit. Image Credit: Brian Kennedy

While astronomers get excited when objects just line up in the sky, transits do have scientific value. Precisely measuring the time length of a transit, and knowing the observer’s location on Earth can allow scientists to accurately measure the distance between Earth and the other planet. From this calculation, we can then accurately measure the distances between the planets and understand the scale of the solar system.

An example of solar eclipse glasses.

How can you view the transit of Mercury? The rules for viewing a transit are very similar for viewing a solar eclipse. The first rule is never look directly at the Sun with your unprotected eyes. Looking at the Sun can damage your eyes quickly and permenantly. The second rule is NEVER EVER look at the Sun through any kind of magnifiying device (like binoculars or a telescope) which does not have a proper solar filter securly installed on the front of it. Looking at the Sun through an unfiltered telescope WILL damage your eyes very quickly and permenantly. If you're not sure if something is a proper filter, do not use it.

For safely viewing the transit you have a couple options. You can use solar eclipse glasses to protect your eyes to look at the Sun. These glasses are frequently made with a thin plastic film that blocks all of the harmful rays from the Sun, and nearly all the optical light from the Sun as well. As a result, the Sun ought to be the only thing that can be seen through these glasses. Before using, inspect the glasses for any scratches or holes in the protective film. If you find any, or any light other than direct sunlight is visible through them, throw those glasses in the garbage. Through eclipse glasses, Mercury should appear as a tiny black dot. But really to see the transit well, you will want to use a telescope.

An example of a solar filter mounted on a telescope.
Image Credit: flickr user Mr.TinDC, CC-BY-ND 2.0

There are a few different kinds of safe telescope options, but the two most common are using a solar filter on a regular telescope, or using a specially made solar telescope. Solar filters are very similar to eclipse glasses, frequently made from the same film, or from glass. These are attached to front the telescope, never the eyepiece, and will protect the telescope and your eyes from the harmful light of the Sun. Solar telescopes are specially designed with filters throughout the telescope to allow one to look directly at the Sun. In fact, the Sun is the only thing you can see through these telescopes. Solar telescopes are usually quite expensive, so your best option is to look for a local astronomy club, school, museum, or planetarium that is hosting a watch party with one.

And it just so happens there is one nearby! We will be observing the Novemeber 11, 2019 transit of Mercury from the Delta College Planetarium in our solar telescope. Provided the weather is clear, we’ll have a telescope set up to safely observe the Sun and Mercury for the duration of the transit. The transit starts at approximately 7:30 am and lasts to about 1pm. We will also have solar eclipse glasses available for visitors to try to spot Mercury with their eyes. It’s the last one until 2032, so don’t miss out.

One last thing before we go: you might have realized that Mars orbits further from the Sun than Earth, and maybe you wonder if Earth ever transits the Sun from Mars. It does! But nobody has ever seen it. The last of these occured in 1984, but there were no operational robots on Mars at the time to photograph it. The next will be in 2084, and there will almost certianly be robots on Mars at that time. Perhaps even people. But if you want to see something really cool, there are times when both Earth (and the Moon) and Venus transit the Sun from Mars at the same time. To see this rare occurance, set your calenders for the year 571,471. You don't want to miss that.

Project Apollo - 50 Years Later

Earthrise from Apollo 12. Image Credit: NASA/JSC

President Kennedy speaks before Congress, May 25, 1961.
Image Credit: NASA

“I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth. No single space project in this period will be more impressive to mankind or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish.”

The silence is the most notable. When the President of the United States speaks before a joint session of Congress, it seems that nearly anything will set the chamber off in a fervor of applause. However, when President John F. Kennedy spoke those words before the assembled chambers on May 25, 1961, it was met with uncharacteristic silence. It was only 3 weeks after Alan Shepard took a Mercury capsule atop a Redstone rocket to the very edge of space to become America’s first astronaut. The United States was playing catch-up after the Soviet Union’s Yuri Gagarin had already orbited the Earth, and Alan Shepard’s 15-minute ballistic visit to space fell well short of that previous accomplishment. Here was the President advocating a plan to do what had seemed impossible for all of human history. It was crazy. It could never happen. When you watch the video of that speech today, you can hear Congress’s reluctance to endorse such an audacious vision.

Astronauts Neil Armstrong and Buzz Aldrin raise the American flag on the surface of the Moon.
July 20, 1969. Image Credit: NASA

Of course, we know it was possible. It did happen. Eight years after the President spoke those words, Neil Armstrong and Buzz Aldrin raised the American flag above the plains of the Sea of Tranquility on the Moon.

There were 11 crewed Apollo flights.
Nine traveled to the Moon.
Image Credit: NASA

The Apollo program was the third and final phase of the America’s strategy in the race to the Moon. Project Mercury sent capsules crewed by only one astronaut into the space, for relatively short durations, just to figure out how to even get there and stay for any length of time. Project Gemini proved that human beings could live in space for extended stays, and actually do meaningful work while there. Project Apollo was the culmination of all this work. The Apollo spacecraft would carry humans away from their own planet for the first time, and land them on an alien world.

Yes, Apollo would complete the challenge set by President Kennedy, but it would do much more. It would bring back pieces of the Moon to help answer question that people have asked since there were people. How old is the Moon, and where did it come from? Did it form at the same time as the Earth? Was it spun off from the molten Earth, like some sort of baby planet? Was it an asteroid that wandered too close and was captured by Earth's gravity?

The 363-foot tall Saturn V Rocket inside
Kennedy Space Center's Vehicle Assembly Building.
Image Credit: NASA

It took hundreds of thousands of people working together to make Apollo successful. From the astronauts who braved the journey, to the engineers who designed the spacecraft and rockets. From the fabricators who meticulously pieced the machine together with precision greater than any clock, to the seamstresses who sewed together the parachutes to slow the capsule to land on Earth.

Each job demanded exacting precision. If any part of the enormous vehicle failed, it could spell disaster for the crew. Each person who worked on the project assumed that responsibility. "It won't fail because of me," became a mantra of Apollo workers. At its peak, the Apollo program employed nearly 400,000 people, and touched every state.

President Kennedy’s speech was prescient in its vision. The Apollo program deserves to be celebrated for its scientific and engineering success. However, the Apollo program’s greatest legacy is as a human moment that transcended national and cultural identities. An estimated 530 million people watched Neil Armstrong take his first steps on the Moon, greater than twice the population of the United States at the time. We were, for a brief moment, one species united by having accomplished the impossible.

Buzz Aldrin's boot leaves a print
in the lunar dust. Image Credit: NASA

For as much as the sight of the Stars and Stripes thrilled the Americans, and stung at their Soviet counterparts, that was not the image that most resonated with the people who witnessed it. It was instead the image of a human being, standing on a alien shore far from home. Ultimately, it didn't matter to the world that the men were Americans. It sufficed that they were humans. Humans, not terribly different from the people who left footprints in the African mud some 100,000 years ago, were now leaving their footprints on the Moon. The humans were capable of greatness.

Astronaut Harrison Schmidt in the Sea of Serenity, December 1972.
This is believed to be the last photograph of an astronaut on the Moon. Image Credit: NASA.

Liftoff of Apollo 4, the first unmanned test
of the Saturn V rocket. Image Credit: NASA

Over the next few years, the Delta College Planetarium and Learning Center will be following along with the Apollo missions as they progressed 50 years ago. We will mark each mission in various different ways through this time. Some missions will be reported on through our social media channels like Facebook. Special programs in the planetarium dome will mark others.

The Delta College Planetarium will be hosting a lunar photography exhibit titled “Many Inspired Steps” throughout the spring and summer of 2019. The exhibit features many pictures taken by astronauts on the barren lunar surface.

On July 20, 2019, the Delta College Planetarium hosted a special event commemorating the 50th anniversary of the first lunar landing.

That does not mark the end though. We will continue to follow along with the Apollo missions on a 50-year delay up through Apollo 17, the last mission to return humans from another world.

So far.

Visions of a Red Planet

Map image:
Percival Lowell, “Globe of Mars, longitude 270º, 1909,”
Hubble Image:
NASA / J. Bell (Cornell) / M. Wolff (SSI)

150 years ago, were I to tell you that someday people would walk on the Moon you might not have believed me. Surrounded by horses and steam, it may well have seemed an impossible dream. Now, nearly 50 years after the first footsteps in lunar dust, our collective perspective has shifted. Today the question isn’t “Will people walk on Mars?” Instead, it’s “Who will be the first?” The technological challenges of traveling to the red planet and returning to the blue are significant, to be sure, but we believe not insurmountable. The biggest question that remains is will it be this generation or the next willing to dedicate the effort to the take the next steps through the solar system.

With this in mind, let us take the occasion of this summer to reflect upon how our knowledge of the red planet has exploded in the last 100 years.

Why this summer? Because geometry.

Both Earth and Mars orbit the Sun in nearly perfect circles, the key word being “nearly”. These "not quite circles" are called ellipses. You can think of an ellipse as sort of a squashed circle. The Sun offset from the center of the orbital ellipses of the planets. The Earth orbits at an average distance from the Sun of about 93 million miles. But because of its elliptical orbit, Earth is actually a little bit closer to the Sun in January, and a little bit further away in July.

The relative positions of Earth and Mars over
a two year period. Image not drawn to scale.

Mars orbits 150 million miles from the Sun, and takes nearly twice as long to orbit the Sun than Earth does. Roughly every two years, the Earth and Mars end up being on the same side of the solar system. When Earth passes Mars in its orbit, Mars will appear directly opposite the Sun in the sky. Astronomers call this “opposition” and when a planet is at opposition it will also be at its closest point to Earth. That’s great news to astronomers who want to look at Mars. Being closer to Earth, Mars will appear bigger and brighter in the telescope.

Sometimes, if astronomers are really lucky, the opposition of Mars will happen just as the Earth is at the furthest point from the Sun in its orbit, and Mars at its nearest point. That cuts a few million more miles off the distance between the two planets, making the red planet appear even brighter in the sky. That’s what happening this summer, making it an excellent time to go out and observe Mars.

What does Mars look like and what can you expect to see this summer?

This photograph of Mars taken during the 2003 opposition
is a good example of the kind of view to expect this summer.
Image Credit: Philipp Salzgeber CC-BY-SA 2.0

Mars is small. It’s a smaller planet than the Earth, but it has about the same land area. If you took all the continents on Earth and crashed them together, you’d get something about the size of Mars. And Mars is far away, even at its closest point. 36 million miles might be spitting distance in the solar system, but it’s still pretty far for human eyes to see. Through a small to medium sized telescope, an observer mostly sees a small, fuzzy, red disc.

Before Cameras were invented, people drew pictures of what they saw to record what was visible in the telescope. They would wait for the brief moments when the air would steady and calm, and then map Mars as accurately as they could. Of course, they were still looking at a small, fuzzy, red disc so they only saw clear glimpses of the planet only briefly. The human brain is incredible at detecting patterns, ocassionally even detecting patterns where no pattern exists. Anyone who’s ever fallen for an optical illusion has experienced this before. Fuzzy data plus a pattern-detecting computer that sometimes gets things wrong can lead to bad conclusions.

The Italian astronomer Giovanni Schiaparelli thought he saw grooves or channels cutting through the Martian surface during the opposition of Mars in 1877. He used the Italian word “canali” to describe them. This word was mistranslated into English not as “channels” but as “canals”. Channels could be formed naturally from the movement of wind or water. But canals? Canals are built by people.

Map of the "Canals" on Mars drawn by Percival Lowell
in his book Mars published 1895.

American businessman Percival Lowell became so obsessed with Schiaparelli’s canals, that he eventually built his own observatory in Arizona, the Lowell Observatory. He believed the canals were a product of a Martian civilization building a vast network of aqueducts. These transported water from the ice caps of the planet to the desert-like regions near the equator. He drew maps of the huge engineering project he believed he saw spider-webbing across the surface. The network of canals didn’t actually exist.

While the scientifc consensus had been that the canals were merely optical illusions for some time, it wasn’t until the Mariner spacecraft missions of the 1960s and 70s that the idea of Martian canals was finally put to rest for good. These probes found no hint of a Martian civilization, but the world they did reveal was perhaps just as interesting as the one some hoped they would find.

Mars was engulfed by a huge dust storm when Mariner 9 entered orbit around the planet in 1971. Mariner 9 was the first spacecraft to orbit another planet, and scientists hoped it would send back the clearest pictures ever seen of Mars. The dust storm made it impossible to see the surface. The scientists waited months for the air to clear. In January 1972, as the dust was still slowly settling out of the atmosphere, Mariner started sending back images. The peaks of four mountains began to peek past the cloud tops. The mountains were tall, very tall. They would have had to tower above the surface. Each had to be about 20 kilometers tall to poke out through the clouds. The tallest was nearly 25 kilometers tall, two and a half times the height of the tallest mountain on Earth. Mars was going to be full of surprises.

Olympus Mons (lower right) is the largest volcano in the solar system at a towering 25 kilometers tall,
two and a half times as tall as Mount Everest.
Image Credit: ESA / DLR / FU Berlin (G. Neukum) / Justin Cowart CC-BY-NC-SA-3.0

As the storm continued to dissipate, the dust lingered in the lowlands. It revealed the presence of a gash in the planet’s crust 8 kilometer deep, four times deeper than Arizona’s Grand Canyon, and nearly as wide as North America. The network of deep chasms that spanned one-quarter the distance around Mars was named the Valles Marineris, or Mariner Valley, after the spacecraft that discovered it. Mariner’s photos revealed a cold desert world, and paved the way for future missions to land on the surface.

The Valles Marineris canyon system stretches over 2,400 miles long
and reaches depths of 23,000 ft.
Image Credit: NASA / JPL-Caltech

This self-portrait taken by Opportunity features the rover still
on its landing stage. The airbags are visible peeking out from behind
the lander petals. Image Credit: NASA / JPL

Each mission to Mars incrementally furthered our understanding of the red planet. Viking showed we could do useful science on the surface. Mars Pathfinder proved we could land cheaply. Mars Odyssey, Mars Global Surveyor, and Mars Reconnaissance Orbiter provided better and better images of the surface from space. Then came the rovers. Landing in January 2004, the Mars Exploration Rovers Spirit and Opportunity were designed to work for 90 Martian days, called 'sols'. Spirit worked for more than 6 years, and finally ceased functioning in 2010 after getting caught in a sand dune. Opportunity is still operating, and as of May 1, 2018 is on sol 5071 of its 90-sol mission. Both rovers sent back evidence supporting the idea that liquid water was present on the surface of Mars sometime in the distant past.

The most recent rover to touch down on the red planet is the Mars Science Laboratory Curiosity. Curiosity landed in 2012 at Gale Crater. Since then it has been climbing the tall mountain located in the center of Gale Crater named Mount Sharp. By analyzing the rock formations that make up Mount Sharp, Curiosity has found evidence that Gale Crater was once filled with a lake of liquid water that may have had conditions suitable for life.

The rim of Gale Crater is visible in the distance in this image taken by the Mars rover Curiostiy.
Image Credit: NASA / JPL-Caltech / MSSS / Damia Bouic
CC-BY-NC-SA-3.0

Each successful mission to Mars has increased our understanding of our neighbor planet, and each one brings us closer to sending the first people to land there. Every photograph sent back has revealed more of that distant world, and has transformed Mars from merely a red point of light in the sky to a place as real as any on the Earth. No longer consigned to the imaginations of science fiction authors, Mars is a destination for future human explorers.

This mosiac showing a full hemisphere of Mars was created from 102 images taken by the Viking orbiters.
The Valles Marineris is visible center, and at the left of the images are the three volcanoes of the Tharsis Plateau.
Image Credit: NASA / JPL-Caltech

As part of observing the opposition of Mars this summer, the Delta College Planetarium and Learning Center will be hosting an exhibition of photographs taken of Mars. Visions of a Red Planet: The Photography of Martian Exploration features stunning images of Mars taken by orbiting spacecraft as well as surface robots. The exhibit runs May 11 through September 1, 2018. Located in the planetarium main lobby, the exhibit is free during all public open hours.

Identifying Meteorites

Photo: Meteor, 8.5.2016 by Migebuff. CC-BY-SA 4.0

There is just something about meteorites. Something deep within us stirs when we hold a rock from “outer space.” Or when we realize that the lump of stone in our hand is billions of years old. It is no wonder that so many people are searching to find their own meteorite. How do you know if you find one? Could that black rock in the garden be a meteorite? It looks interesting. How could you even tell? We at the Delta College Planetarium are here to help give you the knowledge to do a first pass and filter out the regular old earth rocks from the specimens that deserve further scrutiny.

What are meteorites? Are they different from meteors and where do they come from? Astronomers use the word “meteor” to mean one very specific phenomenon; the bright quick streaks of light we occasionally see in the night sky, sometimes called “shooting stars”. Meteors occur when tiny bits of dust and rock slam into the Earth’s atmosphere. The dust or rock itself is called a “meteoroid”. When the meteoroid collides with the atmosphere it quickly rams into the air in front of it. As the air is compressed, it heats up so much that it glows white-hot. This glowing event is a “meteor”.

Most meteoroids end their stories here. The air radiates enough energy to melt and break up the meteoroid. However, some meteoroids are large enough, and strong enough that they survive the shock of entering the Earth’s atmosphere. If a meteoroid survives to the surface, that object graduates to being a “meteorite.”

Basalt is common earth rock that is frequently
misidentified as a meteorite.
Photo: Basalt by James St John. CC-BY 2.0

Meteorites are special because they do not look anything like Earth rocks, chemically speaking. The chemical and physical properties that formed them do not exist on the Earth. Most meteors started their lives in the asteroid belt between the orbits of Mars and Jupiter. In rare cases, a meteorite might have originated from a planetary body, like the Moon or Mars.

A stony meteorite specimen that fell near Tindouf, Algeria.
Photo: NWA869 Meteorite by H Rabb. CC-BY-SA 3.0

Meteorites come in three basic flavors. The first is stony meteorites. These are, true to their name, mainly made of stony materials. These are by far the most common kind of meteorite, but they can be difficult to detect because they frequently look like Earth rocks.

Example of a typical iron meteorite.
Photo: Octahedrite (Canyon Diablo Meteorite) (4.55 Ga) 2
by James St John. CC-BY 2.0

The second kind are iron meteorites. Unsurprisingly, these are made of iron. Far rarer than their stony cousins, iron meteorites are much easier to identify because of just how much iron there is in their chemical makeup.

Stony-iron meteorites feature nodules of minerals
surrounded by iron.
Photo: Pallasite-Esquel-RoyalOntarioMuseum-Jan18-09
by Captmondo. CC-BY-SA 3.0

The third kind of meteorite is sort of a mixture of the two previous types. They get the creative name stony-iron meteorites.

What about the black rock in the garden? Could it be a meteorite? Maybe. Many meteorites share common features that you can check for at home.

One common feature is meteorites tend to be heavy for their size, much heavier than you would expect from an Earth rock. This is because most meteorites have pure iron metal inside of them, even the stony ones. The presence of the iron also means most meteorites will react strongly to a magnet. If a magnet falls off or is only weakly holding on to the rock, then it is probably not a meteorite. In some cases, a stony meteorite might have almost no iron in it, and wouldn't react strongly to a magnet. In those instances, look for other strong indicators of extraterrestrial origin, such as a fusion crust, decribed below.

The iron present in even a stony meteor will have formed into small irregular blobs distributed throughout the specimen. You can scratch the suspected meteorite with a file looking for these blobs. They will appear as bright, shiny metal similar in appearance to chrome. Just a faint metallic sheen will not do, it should shine brightly.

Note how the bright iron blebs are spread randomly through the meteorite.
Iron rich rocks on the earth lack this irregular distribution.
Photo: Fisher by Jon Taylor. CC-BY-SA 2.0

If your suspected meteorite fell from space, it will likely have a layer of fused rock on the outside, called the “fusion crust”. Some meteors break up after the point where a fusion crust would form, exposing some of the inside of the meteorite, but most meteorites will have some of this fusion crust over part or the entire meteorite. The crust forms from the molten rock that develops on the outside as the meteoroid moves through the atmosphere. It will appear dark grey to charcoal black in color. The crust is usually quite thin, only a few millimeters deep. Lines might be present from the flow of hot gasses over the meteorite.

The fine lines in the fusion crust mark where channels of hot gases flowed over
the meteorite while it was entering the atmosphere.
Photo: Allende meteorite, crusted individual, 5g by Jon Taylor. CC-BY-SA 2.0

Smooth divots can appear in the surface of a meteorite, called thumbprints. The surface of a meteorite should still appear relatively smooth and rounded. Remember, this object plunged through the atmosphere. Atmospheric entry will have blasted away any hard angles or sharp edges. There also should be no bubbling or air pockets; these are telltale signs that a rock formed on the Earth.

These divits are called thumbprints because they resemble the mark left behind
when sticking one's thumb into clay.
Photo: Sikhote Alin Meteorite by H. Rabb. CC-BY-SA 3.0

Even though the air sculpts meteorites as they move through the atmosphere, they rarely form aerodynamic shapes. Meteorites are usually irregularly shaped with rounded points, so they are almost never round. Round metallic objects are frequently from human manufactured origins.

Having never been exposed to air, the iron in meteorites is completely unoxidized. Once it becomes exposed to the Earth’s atmosphere, the iron in the meteorite will quickly begin to rust. Suspected meteorites should show signs of this rusting, frequently turning the common rusty red color.

You can also perform a streak test. Take an inexpensive, unglazed, white ceramic tile from a home improvement store and drag the suspected meteorite across the tile. What color streak did the rock leave behind? If the streak is brown, it might be a meteorite. Meteorites produce a brown colored powder when finely ground. If the color is red or black, it is unlikely to be a meteorite and is probably some form of Earth rock.

Does it mean that a rock that passes all these tests is a meteorite? Meteorites are quite rare and Earth rocks can masquerade as them well enough to pass these tests. Ultimately, the only way to know for sure is to test the sample’s chemical composition in a laboratory.