Martian Dust Devils

 

Martian dust devils are much like tornadoes on Earth. Both storms form the same way, but what distinguishes these dust devils from the tornadoes on Earth is that they are much bigger ( 1-2 km across and 8-10 km wide!) and the fact that dust devils occur much more frequently on Mars than tornadoes do on Earth. Although the exact frequency is not known, during the summer and spring months on Mars, around half a dozen dust devils can be spotted each day. This is due to the extreme variance in temperatures on Mars between daytime (where it reaches 20 degrees Celsius) and nighttime (which cools to around -90 degrees Celsius). Because of the varying temperature, the ground becomes hotter than the air above it and the heated air near the ground rises as the cooler air begins to fall. This coupled with a horizontal wind forms the vertical columns which forms the beginning of a dust devil. Despite the fact that dust devils are much bigger than tornadoes, because of Mars’s lower atmospheric pressure, the winds from the dust devils would be bearable to a person standing in one, but the high speed at which the sand is being moved would be much more dangerous.

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Voyager 2

August 20, 1977. The flyby-type probe Voyager 2 was launched from Earth, destined to explore our Solar System and beyond. Passing by Jupiter, Saturn, Uranus, and Neptune, Voyager 2 carried with it instruments to relay close-up images of these Jovian planets, and a message from Earth to be read and listened to by those who may receive the probe far in the future after it departs from our Solar System. These messages are carried by a golden record – the golden record – inscribed with sounds from our planet including greetings in fifty-five human languages in addition to a whale greeting, and images and music from different cultures. Etched onto the protective cover is a symbolic representation of instructions depicting how to use the included equipment to play the record as well as images explaining where the probe originated by means of a pulsar map (lower left of record) that shows the Sun’s location relative to the fourteen nearest pulsars to Earth.

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A Voyager in the Solar System: The Story of the Voyager I and II

Two twins. Exploring where no other spacecraft has ever explored before. This was the goal that NASA set out to accomplish when they launched the Voyager spacecrafts. At least, this is what their missions came to be. However, it is not just the missions themselves that make them famous, but also what they carry for humanity. However, let us not get ahead of ourselves without a bit of history.

The Voyager 1 and Voyager 2 were sent into space by NASA in 1977 from Cape Canaveral, FL, in order to survey Jupiter, Saturn, Saturn’s rings, and large moons that surround the two planets. Voyagers 1 and 2 were sent 16 days apart from each other, and were only built to last 5 years. However, the technology proved resilient in space, and today the Voyager spacecrafts still report back to mission control.

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Voyager 1 on left; Voyager 2 on right. Image sourced from annesastronomynews

When it was found that the Voyager spacecrafts could continue doing research, NASA made the decision to direct the spacecraft’s resources to two locations. Voyager 1 was to be sent deep into interstellar space, and so from the end of its original mission the probe has been travelling deep into space. On August 25, 2012, it escaped the solar system and officially hit interstellar space. Voyager 2, on the other hand, was to be used to survey Neptune and Uranus, and is still the only man-made object to date to survey the two ice planets. Now all of this information is nice and dandy, but it leads to an important premise.

Before the Voyager spacecrafts were sent, a decision was made to include some information about humanity on the spacecrafts, just in case alien life happened to stumble upon it. This culminated in the creation of a golden record. Two copies of the record were made for each one of the Voyagers, but their contents are what continue to intrigue those that look into the topic.

On the front side of the record, seen as the left side of the featured image, are a variety of images etched into the golden surface. The images are supposed to depict the origin of the spacecraft as well as how the record is to be played. On the backside of the record are 115 images encoded in analogue that are supposed to represent Earth and human life. The rest of the record contains greetings and language starting with the Sumerian language (spoken 6000 years ago) to greetings today. Beyond that, it also includes 90 minutes of music hand selected from a variety of genres, both classical and modern to the time. It would intrigue some of you to know that the music, greetings, and images were selected by a committee at NASA headed by the famous physicist Carl Sagan.

So, what does this mean to you? Should we be afraid of broadcasting ourselves to alien civilizations? Stephen Hawking says yes, but others argue that it is important to learn about the rest of our universe. When selecting these images and sounds, Sagan and his team sought to reflect every facet of human life. So, some images are happy, sad, strange, and even anatomical. As a man of science, Sagan made sure to include a representation of the hydrogen atom and the makeup of the DNA molecule, two of the most profound discoveries in science. I have went ahead and placed an image below, but you can view all 115 at the Voyager website.

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One of the more interesting photos encoded in these disks. Sourced from NASA

It may be the case that these spacecrafts are never found. That they will live out the rest of their existence floating in space, just like any other asteroid, or planet, or solar system, or even galaxy. But on the off-chance that another being does see it, we give a signal of hope. A hope that we are not alone in the universe. A hope that there is something more beyond us, and something more beyond them. Today, Voyager 1 travels alone in deep interstellar space, doing what it was meant to do. But, in doing this, it remains alone in the vastness of space. One day, its battery will have no power left to run its critical processes and Voyager 1 will simply float in space, carrying a bit of humanity with it. I think that, for a moment, we all feel like Voyager 1. Let this piece, selected by Sagan, resonate as we think about the loneliness of being a single spec of humanity within a sea of other worlds.

Featured image sourced from the Smithsonian

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Fusion vs. Fission

The nuclear energy can be generated in two ways – fusion and fission. Both fusion and fission energy are generated by altering atoms. What is the difference between fusion and fission? And which way will generate more energy?

As the word “fission” means separate a thing into different parts, nuclear fission means releases energy by splitting atoms. Nuclear fission happens when an unstable isotope is contacted by some high-speed particles. At this time, the unstable isotope is accelerated and then break into small particles.

Unlike “fission”, nuclear fusion means “fusing” several particles into “one”. Nuclear fusion happens when several low-mass particles compress together and release the neutron they do not need anymore. By uniting different particles and releasing neutron, a huge amount of energy is released.

Although nuclear fission can generate higher energy than nuclear fusion, we can hardly found any nuclear fission in our sun. The reason is that nuclear fission requires a particle with enough mass so that it can be “split” into several particles. However, the major element inside Sun are Hydrogen and Helium, which are both low-mass particles. Therefore, the major nuclear energy inside the sun is generated by nuclear fusion.

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Nuclear Fusion, pic source 
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Climate Change from the Perspective of Astronomy: Venus and the Earth

Today we hear about climate change pretty often. Whether it’s politicians debating on policy or the “please recycle” signs on the backs of plastic products, the reality of pollution and the other bad ways humans have influenced the environment is hard to ignore. CO2 emissions  and the greenhouse effect are common themes in this topic, since they pose the most devastating yet entirely feasible threat to life on earth. From the many angles that one can look at pollution and climate change, whether that’s from politics, climate science, or anthropology, or marine biology, one of the most informative angles come from the astronomical perspective.

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Venus and Earth. Wikipedia

The reason to be so concerned about carbon dioxide (CO2) emissions becomes undeniably clear when you compare the Earth to Venus. Just a little close to the sun, Venus is otherwise very similar to Earth in size and composition, yet it is completely uninhabitable. Although Venus has volcanoes and perhaps tectonic plates just like its sister, Earth, its mean surface temperature is a whopping 735 Kelvin! That’s 462 °C or 863 °F, much to hot for habitation. Why is Venus so hot? Its atmosphere is composed of 96% CO2, compared to the Earth’s almost complete lack of CO2 in its atmosphere. When an atmosphere has lots of CO2, then the Greenhouse Effect causes the planet to retain its heat and get hotter and hotter. So where is all the Earth’s CO2? Well, much of it is stored in the ground in places such as coal and oil, and as we burn them as sources of energy it could potentially put more CO2 into the atmosphere than the Earth could handle and snowball (no pun intended) out of control, causing its temperature to get higher and higher until it is uninhabitable. For the astronomer, then, caring about climate change and getting CO2 emissions under control is about keeping the Earth from ever looking like Venus, staying blue, white, and beautiful instead of a waterless wasteland.

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The Death of the Sun

Unfortunately, our Solar System will not exist forever–our Sun’s lifespan is indeed finite. Sunlike stars stay on the main sequence for approximately 10 billions years. In other words, this is about how long the Sun will shine. The Sun is about 4.6 billion years old, so we may expect about 5.4 billion more years of sunshine on Earth. But here’s the problem: as the Sun dies, it will catastrophically swell to a radius that will destroy most of its orbiting planets. In this so called “red giant phase”, all the hydrogen of the star has been fused to helium, and so heavier elements begin fusing in the core.

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An artist impression of the red giant phase

In this phase, the Sun will expand to achieve a radius of more than twice the distance between the Sun’s center and the Earth. In other words, our planet will be swallowed up by the Sun. Following this red giant phase, the Sun will shed its outer mass in a planetary nebula, leaving behind a small, superdense white dwarf (essentially the corpse of the star) at the center.

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Almost InSight

InSight spacecraft solar array deployment

InSight is short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, and is NASA’s next big spacecraft. A little contrived, but its memorable. InSight is a Mars lander designed to study the inside of Mars: the crust, mantle, and core. It does so by measuring the planet’s seismology, heat flow, and precision tracking. By studying these variables, the mission will seek to uncover how a rocky body forms and evolves to become a planet. Its secondary mission will be to determine the level of tectonic activity on Mars. Mars has low levels of geological activity, which means that it well preserves the record of its formation and can provide valuable insight (get it) into how the terrestrial planets formed.

The lander was primarily built by Lockheed Martin, who built NASA’s first Mars lander in 1976. Lockheed Martin built most of the lander in Colorado, and completed most of the manufacturing three years ago.  NASA originally hoped to launch in May 2016, but ran into technical difficulties with one of the instruments. The mission was pushed to 2018, the next time when Earth and Mars’ orbits are lined up.

The launch period is set for May 5, 2018. InSight will launch from a United Launch Alliance Atlas V rocket, and is scheduled to arrive on Mars November 26, 2018.

 

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Measuring the Interior of the Earth

It is very hard to drill to the deepest part of the Earth. However, there are some indirect measurements that allow us to know limited information about the interior structure of the Earth. One of those is the measurement of seismic waves.

By knowing the characteristic of seismic waves, we are able to identify the properties of the material that the waves pass through since different types of material affect the speed of the waves by different amount. Then, the precise measurement is based on the duration that certain seismic waves travel after an earthquake, indicating the specific properties of the materials that the waves encountered.

There are two types of seismic waves: P-waves and S-waves. P-waves are able to pass through solid and liquid materials, whereas S-waves are only able to pass through solid material. With the above information, the structure of the interior of the Earth can be calculated, which has a liquid outer core and a solid inner core.

 

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Picture from Andres Robotics and Science

 

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Nuclear Fusion

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Nuclear Fusion refers to the nuclear reaction in which atomic nuclei of low atomic number elements fuse to form a heavier nucleus.  This reactions releases energy and is how the sun and other stars generate light and heat.  Energy is produced during the smashing of the lighter atoms, which is most easily achieved on Earth by combining two isotopes of hydrogen: deuterium and tritium.  Nuclear fusion yields energy because the mass of the combination will be less than the sum of the masses of the individual nuclei,. If the combined nuclear mass is less than that of iron at the peak of the binding energy curve, the nuclear particles will be more tightly bound than they were in the light nuclei, and that decrease in mass is compensated in the form of energy according to the Einstein relationship.

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Nuclear Waste: a closer look

Every year, approximately 20% of the energy generated by the United States comes from nuclear power. Throughout the years, our consumption of nuclear power has brought with it over 90,000 metric tons of nuclear waste. 97% of nuclear waste in the world has been classified as low- or intermediate- level waste (LLW or ILW) while the remaining 3% has been classified as high-level waste (HLW). The difference in the levels refers to the radioactive content and half-life (i.e., the time needed for a source to lose half of its radioactivity) of the waste.

Low-level waste (LLW) contains the minimal amount of radioactivity. It often refers to the type of waste that is generated from daily operations in hospitals, laboratories, and various industries. It can range from contaminated gloves used in university projects to parts of a nuclear power plant. LLW is generally disposed of either by waiting for its radioactivity to drop low enough to dispose of as normal waste or amassed and stored in government-approved containers close to the Earth’s surface.

Intermediate-level waste (ILW) has higher radioactive levels and requires shielding when handled. It often refers to the less radioactive byproducts of nuclear energy operations and can also include parts of a nuclear power plant. ILW disposal normally requires the waste to be reprocessed and incorporated into non-radioactive objects like cement or bitumen before being stored in a container. It is also stored close to the Earth’s surface.

High-level waste (HLW) contains the most radioactivity. It often refers to the most radioactive byproducts of nuclear energy operations. HLW is generally stored at nuclear reactor sites until it can be safely transferred to government-approved containers composed of concrete, steel, and heavy elements in the periodic table such as lead.

Currently, there is no permanent disposal solution for nuclear waste. The only way radioactive materials can become harmless to humans is through decay. For high-level waste, this can mean hundreds of thousands of years.

There is much concern today over the safety and conceivability of generating more nuclear waste. One of the most important considerations is the location of permanent disposal sites. Radioactive leakage can have devastating results, as we have seen from Russia’s Chernobyl and Japan’s Fukushima nuclear accidents.

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The Chernobyl nuclear disaster was one of the most disastrous nuclear accidents in history. As with other nuclear disasters, much of the surrounding area still lies abandoned due to the overwhelming radioactive levels.

Although places such as the Yucca mountain site in Nevada have lobbied hard for a license for permanent nuclear disposal, there is still, as of to date, no permanent nuclear disposal site in the United States. Part of this is due to public perception of nuclear activity. Nuclear testing sites during World War II in New Mexico have still had a lingering effect on the residents of the surrounding areas even after 70 years. Despite the potential economical stimulation of nuclear power production, many regions of the United States are fearful of similar results.

One of the most ambitious proposals for the disposal of nuclear waste is to launch it into space. Despite initial interest in the 1970’s, many programs have since lost funding due to the associated high cost and risk aspect of the launch failing and the material returning to Earth.

Today, global nuclear waste is projected increase to about 140,000 metric tons over the next several decades. While there is still ambiguity surrounding the problem of disposal, many organizations are working to find a safe and permanent solution. A brief strategic plan by the Department of Energy for nuclear waste disposal within the United States can be found here.

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