Solar System: 10 Things To Know This Week

Oldest recorded solar eclipse helps date the Egyptian pharaohs

UNIVERSITY OF CAMBRIDGE—Researchers have pinpointed the date of what could be the oldest solar eclipse yet recorded. The event, which occurred on 30 October 1207 BC, is mentioned in the Bible, and could have consequences for the chronology of the ancient world.

Using a combination of the biblical text and an ancient Egyptian text, the researchers were then able to refine the dates of the Egyptian pharaohs, in particular the dates of the reign of Ramesses the Great. The results are published in the Royal Astronomical Society journal Astronomy & Geophysics.

The biblical text in question comes from the Old Testament book of Joshua and has puzzled biblical scholars for centuries. It records that after Joshua led the people of Israel into Canaan - a region of the ancient Near East that covered modern-day Israel and Palestine - he prayed: “Sun, stand still at Gibeon, and Moon, in the Valley of Aijalon. And the Sun stood still, and the Moon stopped, until the nation took vengeance on their enemies.” Read more.

What are brown dwarfs?

In order to understand what is a brown dwarf, we need to understand the difference between a star and a planet. It is not easy to tell a star from a planet when you look up at the night sky with your eyes. However, the two kinds of objects look very different to an astronomer using a telescope or spectroscope. Planets shine by reflected light; stars shine by producing their own light. So what makes some objects shine by themselves and other objects only reflect the light of some other body? That is the important difference to understand – and it will allow us to understand brown dwarfs as well.

As a star forms from a cloud of contracting gas, the temperature in its center becomes so large that hydrogen begins to fuse into helium – releasing an enormous amount of energy which causes the star to begin shining under its own power. A planet forms from small particles of dust left over from the formation of a star. These particles collide and stick together. There is never enough temperature to cause particles to fuse and release energy. In other words, a planet is not hot enough or heavy enough to produce its own light.

Brown dwarfs are objects which have a size between that of a giant planet like Jupiter and that of a small star. In fact, most astronomers would classify any object with between 13 times the mass of Jupiter and 75 times the mass of Jupiter to be a brown dwarf. Given that range of masses, the object would not have been able to sustain the fusion of hydrogen like a regular star; thus, many scientists have dubbed brown dwarfs as “failed stars”.

A Trio of Brown Dwarfs

This artist’s conception illustrates what brown dwarfs of different types might look like to a hypothetical interstellar traveler who has flown a spaceship to each one. Brown dwarfs are like stars, but they aren’t massive enough to fuse atoms steadily and shine with starlight – as our sun does so well.

On the left is an L dwarf, in the middle is a T dwarf, and on the right is a Y dwarf. The objects are progressively cooler in atmospheric temperatures as you move from left to right. Y dwarfs are the newest and coldest class of brown dwarfs and were discovered by NASA’s Wide-field Infrared Survey Explorer, or WISE. WISE was able to detect these Y dwarfs for the first time because it surveyed the entire sky deeply at the infrared wavelengths at which these bodies emit most of their light. The L dwarf is seen as a dim red orb to the eye. The T dwarf is even fainter and appears with a darker reddish, or magenta, hue. The Y dwarf is dimmer still. Because astronomers have not yet detected Y dwarfs at the visible wavelengths we see with our eyes, the choice of a purple hue is done mainly for artistic reasons. The Y dwarf is also illustrated as reflecting a faint amount of visible starlight from interstellar space.

In this rendering, the traveler’s spaceship is the same distance from each object. This illustrates an unusual property of brown dwarfs – that they all have the same dimensions, roughly the size of the planet Jupiter, regardless of their mass. This mass disparity can be as large as fifteen times or more when comparing an L to a Y dwarf, despite the fact that both objects have the same radius. The three brown dwarfs also have very different atmospheric temperatures. A typical L dwarf has a temperature of 2,600 degrees Fahrenheit (1,400 degrees Celsius). A typical T dwarf has a temperature of 1,700 degrees Fahrenheit (900 degrees Celsius). The coldest Y dwarf so far identified by WISE has a temperature of less than about 80 degrees Fahrenheit (25 degrees Celsius).

Sources: starchild.gsfc.nasa.gov & nasa.gov 

 image credit: NASA / JPL-Caltech

Spacewalk Recap Told in GIFs

Friday, Oct. 20, NASA astronauts Randy Bresnik and Joe Acaba ventured outside the International Space Station for a 6 hour and 49 minute spacewalk. Just like you make improvements to your home on Earth, astronauts living in space periodically go outside the space station to make updates on their orbiting home.

During this spacewalk, they did a lot! Here’s a recap of their day told in GIFs…

All spacewalks begin inside the space station. Astronauts Paolo Nespoli and Mark Vande Hei helped each spacewalker put on their suit, known as an Extravehicular Mobility Unit (EMU).

They then enter an airlock and regulate the pressure so that they can enter the vacuum of space safely. If they did not regulate the pressure safely, the astronauts could experience something referred to as “the bends” – similar to scuba divers.

Once the two astronauts exited the airlock and were outside the space station, they went to their respective work stations.

Bresnik replaced a failed fuse on the end of the Dextre robotic arm extension, which helps capture visiting vehicles.

During that time, Acaba set up a portable foot restraint to help him get in the right position to install a new camera.

While he was getting set up, he realized that there was unexpected wearing on one of his safety tethers. Astronauts have multiple safety mechanisms for spacewalking, including a “jet pack” on their spacesuit. That way, in the unlikely instance they become untethered from the station, the are able to propel back to safety.

Bresnik was a great teammate and brought Acaba a spare safety tether to use.

Once Acaba secured himself in the foot restraint that was attached to the end of the station’s robotic arm, he was maneuvered into place to install a new HD camera. Who was moving the arm? Astronauts inside the station were carefully moving it into place!

And, ta da! Below you can see one of the first views from the new enhanced HD camera…(sorry, not a GIF).

After Acaba installed the new HD camera, he repaired the camera system on the end of the robotic arm’s hand. This ensures that the hand can see the vehicles that it’s capturing.

Bresnik, completed all of his planned tasks and moved on to a few “get ahead” tasks. He first started removing extra thermal insulation straps around some spare pumps. This will allow easier access to these spare parts if and when they’re needed in the future.

He then worked to install a new handle on the outside of space station. That’s a space drill in the above GIF. 

After Acaba finished working on the robotic arm’s camera, he began greasing bearings on the new latching end effector (the arm’s “hand”), which was just installed on Oct. 5.

The duo completed all planned spacewalk tasks, cleaned up their work stations and headed back to the station’s airlock. 

Once safely inside the airlock and pressure was restored to the proper levels, the duo was greeted by the crew onboard. 

They took images of their spacesuits to document any possible tears, rips or stains, and took them off. 

Coverage ended at 2:36 p.m. EDT after 6 hours and 49 minutes. We hope the pair was able to grab some dinner and take a break!

You can watch the entire spacewalk HERE, or follow @Space_Station on Twitter and Instagram for regular updates on the orbiting laboratory. 

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A slow-motion animation of the Crab Pulsar taken at 800 nm wavelength (near-infrared) using a Lucky Imaging camera from Cambridge University, showing the bright pulse and fainter interpulse.

Credit: Cambridge University Lucky Imaging Group

Cassini Mission: What’s Next?

It’s Friday, Sept. 15 and our Cassini mission has officially come to a spectacular end. The final signal from the spacecraft was received here on Earth at 7:55 a.m. EDT after a fateful plunge into Saturn’s atmosphere.

After losing contact with Earth, the spacecraft burned up like a meteor, becoming part of the planet itself.

Although bittersweet, Cassini’s triumphant end is the culmination of a nearly 20-year mission that overflowed with discoveries.

But, what happens now?

Mission Team and Data

Now that the spacecraft is gone, most of the team’s engineers are migrating to other planetary missions, where they will continue to contribute to the work we’re doing to explore our solar system and beyond.

Mission scientists will keep working for the coming years to ensure that we fully understand all of the data acquired during the mission’s Grand Finale. They will carefully calibrate and study all of this data so that it can be entered into the Planetary Data System. From there, it will be accessible to future scientists for years to come.

Even beyond that, the science data will continue to be worked on for decades, possibly more, depending on the research grants that are acquired.

Other team members, some who have spent most of their career working on the Cassini mission, will use this as an opportunity to retire.

Future Missions

In revealing that Enceladus has essentially all the ingredients needed for life, the mission energized a pivot to the exploration of “ocean worlds” that has been sweeping planetary science over the past couple of decades.

Jupiter’s moon Europa has been a prime target for future exploration, and many lessons during Cassini’s mission are being applied in planning our Europa Clipper mission, planned for launch in the 2020s.

The mission will orbit the giant planet, Jupiter, using gravitational assists from large moons to maneuver the spacecraft into repeated close encounters, much as Cassini has used the gravity of Titan to continually shape the spacecraft’s course.

In addition, many engineers and scientists from Cassini are serving on the new Europa Clipper mission and helping to shape its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer team are developing an extremely sensitive, next-generation version of their instrument for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will be invaluable to Europa Clipper, should plume activity be confirmed on Europa.

In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include robotic explorers to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.

Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent recommendations from a group of planetary scientists shows interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an potential Saturn atmospheric probe.

A variety of potential mission concepts are discussed in a recently completed study — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.

Learn more about the Cassini mission and its Grand Finale HERE.

Follow the mission on Facebook and Twitter for the latest updates.

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Reinventing the Wheel

Planning a trip to the Moon? Mars? You’re going to need good tires…

Exploration requires mobility. And whether you’re on Earth or as far away as the Moon or Mars, you need good tires to get your vehicle from one place to another. Our decades-long work developing tires for space exploration has led to new game-changing designs and materials. Yes, we’re reinventing the wheel—here’s why.

Wheels on the Moon

Early tire designs were focused on moving hardware and astronauts across the lunar surface. The last NASA vehicle to visit the Moon was the Lunar Roving Vehicle during our Apollo missions. The vehicle used four large flexible wire mesh wheels with stiff inner frames. We used these Apollo era tires as the inspiration for new designs using newer materials and technology to better function on a lunar surface.

Up springs a new idea

During the mid-2000s, we worked with industry partner Goodyear to develop the Spring Tire, an airless compliant tire that consists of several hundred coiled steel wires woven into a flexible mesh, giving the tires the ability to support high loads while also conforming to the terrain. The Spring Tire has been proven to generate very good traction and durability in soft sand and on rocks.

Spring Tires for Mars

A little over a year after the Mars Curiosity Rover landed on Mars, engineers began to notice significant wheel damage in 2013 due to the unexpectedly harsh terrain. That’s when engineers began developing new Spring Tire prototypes to determine if they would be a new and better solution for exploration rovers on Mars.

In order for Spring Tires to go the distance on Martian terrain, new materials were required. Enter nickel titanium, a shape memory alloy with amazing capabilities that allow the tire to deform down to the axle and return to its original shape.

These tires can take a lickin’

After building the shape memory alloy tire, Glenn engineers sent it to the Jet Propulsion Laboratory’s Mars Life Test Facility. It performed impressively on the punishing track.

Why reinvent the wheel? It’s worth it.

New, high performing tires would allow lunar and Mars rovers to explore greater regions of the surface than currently possible. They conform to the terrain and do not sink as much as rigid wheels, allowing them to carry heavier payloads for the same given mass and volume. Also, because they absorb energy from impacts at moderate to high speeds, there is potential for use on crewed exploration vehicles which are expected to move at speeds significantly higher than the current Mars rovers.

Airless tires on Earth

Maybe. Recently, engineers and materials scientists have been testing a spinoff tire version that would work on cars and trucks on Earth. Stay tuned as we continue to push the boundaries on traditional concepts for exploring our world and beyond.  

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Curiosity drill site reveals that under its red surface, Mars is grey-blue

via reddit

Curiosity Rover: Five Years on Mars

The evening of August 5, 2012…five years ago…our Mars Curiosity rover landed on the Red Planet. 

Arriving at Mars at 10:32 p.m. PDT (morning of Aug 6 EDT), this rover would prove to be the most technologically advanced rover ever built.

Curiosity used a series of complicated landing maneuvers never before attempted. 

The specialized landing sequence, which employed a giant parachute, a jet-controlled descent vehicle and a daring “sky crane” maneuver similar to rappelling was devised because testing and landing techniques used during previous rover missions could not safely accommodate the much larger and heavier rover.

Curiosity’s mission: To determine whether the Red Planet ever was, or is, habitable to microbial life.

The car-size rover is equipped with 17 cameras, a robotic arm, specialized instruments and an on-board laboratory.

Let’s explore Curiosity’s top 5 discoveries since she landed on Mars five years ago…

1. Gale Crater had conditions suitable for life about 3.5 billion years ago

In 2013, Curiosity’s analysis of a rock sample showed that ancient Mars could have supported living microbes. Scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon – some of the key chemical ingredients for life – in the powder Curiosity drilled out of a sedimentary rock near an ancient stream bed in Gale Crater.

Later, in 2014, Curiosity discovered that these conditions lasted for millions of years, perhaps much longer. This interpretation of Curiosity’s findings in Gale Crater suggests ancient Mars maintained a climate that could have produced long-lasting lakes at many locations on the Red Planet.

2. Organic molecules detected at several locations

In 2014, our Curiosity rover drilled into the Martian surface and detected different organic chemicals in the rock powder. This was the first definitive detection of organics in surface materials of Mars. These Martian organics could either have formed on Mars or been delivered to Mars by meteorites. 

Curiosity’s findings from analyzing samples of atmosphere and rock powder do not reveal whether Mars has ever harbored living microbes, but the findings do shed light on a chemically active modern Mars and on favorable conditions for life on ancient Mars.

3. Present and active methane in Mars’ atmosphere

Also in 2014, our Curiosity rover measured a tenfold spike in methane, an organic chemical, in the atmosphere around the planet. This temporary increase in methane tells us there must be some relatively localized source.

Researchers used Curiosity’s onboard Sample Analysis at Mars (SAM) laboratory a dozen times in a 20-month period to sniff methane in the atmosphere. During two of those months, in late 2013 and early 2014, four measurements averaged seven parts per billion.

4. Radiation could pose health risks for humans

Measurements taken by our Curiosity rover since launch have provided us with the information needed to design systems to protect human explorers from radiation exposure on deep-space expeditions in the future. Curiosity’s Radiation Assessment Detector (RAD) was the first instrument to measure the radiation environment during a Mars cruise mission from inside a spacecraft that is similar to potential human exploration spacecraft.

The findings indicate radiation exposure for human explorers could exceed our career limit for astronauts if current propulsion systems are used. These measurements are being used to better understand how radiation travels through deep space and how it is affected and changed by the spacecraft structure itself. This, along with research on the International Space Station are helping us develop countermeasures to the impacts of radiation on the human body.

5. A thicker atmosphere and more water in Mars past

In 2015, Curiosity discovered evidence that has led scientists to conclude that ancient Mars was once a warmer, wetter place than it is today. 

To produce this more temperate climate, several researchers have suggested that the planet was once shrouded in a much thicker carbon dioxide atmosphere. You may be asking…Where did all the carbon go?

The solar wind stripped away much of Mars’ ancient atmosphere and is still removing tons of it every day. That said, 3.8 billion years ago, Mars might have had a moderately dense atmosphere, with a surface pressure equal to or less than that found on Earth.

Our Curiosity rover continues to explore the Red Planet today. On average, the rover travels about 30 meters per hour and is currently on the lower slope of Mount Sharp.

Get regular updates on the Curiosity mission by following @MarsCuriosity on Twitter.

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Composed of gas and dust, the pictured pillar resides in a tempestuous stellar nursery called the Carina Nebula, located 7500 light-years away in the southern constellation of Carina.

Credit: NASA, ESA and the Hubble SM4 ERO Team

The missing links between galaxies have finally been found. This is the first detection of the roughly half of the normal matter in our universe – protons, neutrons and electrons – unaccounted for by previous observations of stars, galaxies and other bright objects in space.