Halos on Mars

By JoEllen McBride, PhD

Curiosity Discovery Suggests Early Mars Environment Suitable for Life Longer Than Previously Thought.

 

We have been searching desperately for evidence of life on Mars since the first Viking lander touched down in 1976. So far we’ve come up empty-handed but a recent finding from the Curiosity rover has refueled scientists’ hopes.

 

NASA’s Curiosity rover is currently puttering along the Martian surface in Gale Crater. Its mission is to determine whether Mars ever had an environment suitable for life. The clays and by-products of reactions between water and sulfuric acid (a.k.a. sulfates) that fill the crater are evidence that it once held a lake that dried up early in the planet’s history. Using its suite of instruments, Curiosity is digging, sifting and burning the soil for clues to whether the wet environment of a young Mars could ever give rise to life.

 

On Tuesday, scientists announced that they discovered evidence that groundwater existed in Gale Crater long after the lake dried up. Curiosity noticed lighter colored rock surrounding fractures in the crater which scientists recognized as a tell-tale sign of groundwater. As water flows underground on Earth, oxygen atoms from the water combine with other minerals found in the rock. The newly-formed molecules are then transported by the flowing water and absorbed by the surrounding rock. This process creates ‘halos’ within the rock that often have different coloration and composition than the original rock.

 

Curiosity used its laser instrument to analyze the composition of the lighter colored rock in Gale Crater and reported that it was full of silicates. This particular region of the crater contains rock that was not present at the same time as the lake and does not contain the minerals necessary to produce silicates. So the only way these silicates could be present is if they were transported there from older rock. Using what they know about groundwater processes on Earth, NASA scientists determined that groundwater must have reacted with silicon present in older rock creating the silicates. These new minerals then flowed to the younger bedrock and seeped in resulting in the halos Curiosity discovered. The time it would take these halos to form provide strong evidence that groundwater persisted in Gale Crater much longer than previously thought.

 

Credit: NASA/JPL-Caltech Image from Curiosity of the lighter colored halos surrounding fractures in Gale Crater.
Credit: NASA/JPL-Caltech Image from Curiosity of the lighter colored halos surrounding fractures in Gale Crater.

This news also comes on the heels of the first discovery of boron by Curiosity on Mars. Boron on Earth is present in dried-up, non-acidic water beds. Finding boron on Mars suggests that the groundwater present in Gale Crater was most likely at a temperature and acidity suitable for microbial life. The combination of the longevity of groundwater and its acceptable acidity greatly increases the window for microbial life to form on young Mars.

 

These two discoveries have not only extended the time-frame for the habitability of early Mars but lead one to wonder where else groundwater was present on the planet. We hopefully won’t have to wait too long to find out. Curiosity is still going strong and NASA has already begun work on a new set of exploratory Martian robots. The next rover mission to Mars is set to launch in 2020 and will be equipped with a drill that will remove core samples of Martian soil. The samples will be stored on the planet for retrieval at a later date. What (or who) will be sent to pick up the samples is still being determined.

 

Although we haven’t found evidence for life on Mars, the hope remains. It appears Mars had the potential for life at the same time in its formation as Earth. We just have to continue looking for organic signatures in the Martian soil or determine what kept life from getting its start on the Red Planet.

 

Want to Watch History Burn? Check Out a Meteor Shower!

 

By JoEllen McBride, PhD

 

Fireballs streaking across the sky. Falling or shooting stars catching your eye. Meteors have fascinated humans as long as we’ve kept records. Depending on the time of year, on a clear night, you can see anywhere from 2 to 16 meteors enter our atmosphere and burn up right before your eyes. If you really want a performance, you should look up during one of the many meteor showers that happen throughout the year. These shows can provide anywhere from 10 to 100 meteors an hour! But what exactly is burning up to create these cosmic showers?

 

To answer this question we need to go back in time to the formation of our solar system. Our galaxy is full of dust particles and gas. If these tiny particles get close enough they’ll be gravitationally attracted and forced to hang out together. The bigger a blob of gas and dust gets, the more gas and dust it can attract from its surroundings. As more and more particles start occupying the same space, they collide with each other causing the blob to heat up. At a high enough temperature the ball of now hot gas can fuse Hydrogen and other elements which sustains the burning orb. Our Sun formed just like this, about 5 billion years ago.

 

Any remaining gas and dust orbiting our newly created Sun coalesced into the eight planets and numerous dwarf planets and asteroids we know of today. Even though the major planets have done a pretty good job clearing out their orbits of large debris, many tiny particles and clumps of pristine dust remain and slowly orbit closer and closer to the Sun. If these 4.5 billion year old relics cross Earth’s path, our planet smashes into them and they burn up in our atmosphere. These account for many of the meteors that whiz through our atmosphere unexpectedly.

 

The predictable meteor showers, on the other hand, are a product of the gravitational influence of the larger gas giant planets. These behemoths forced many of the smaller bodies that dared to cross them out into the furthest reaches of our solar system. Instead of being kicked out of the solar system completely, a few are still gravitationally bound to the Sun in orbits that take them from out beyond the Kuiper belt to the realm of the inner planets. As these periodic visitors approach our central star, their surfaces warm, melting ice that held together clumps of ancient dust. The closer the body gets to the Sun, the more ice melts– leaving behind a trail of particulates. We humans see the destruction of these icy balls as beautiful comets that grace our night skies periodically. But the trail of dust remains long after the comet heads back to edge of our solar system.

 

The dusty remains of our cometary visitors slowly orbit the Sun along the comet’s path. There are a few well-known dust lanes that our planet plows into annually. Some of these showers produce exciting downpours with over a hundred meteors an hour and others barely produce a drip. April begins the meteor shower season and the major events for 2017 are listed below.

Shower Dates

Peak Times

(UT)

Moon Phase At Peak Progenitor
Range Peak
Lyrid (N) Apr 16-25 Aprl 22 12:00 Crescent Thatcher 1861 I
Eta Aquarid (S) Apr 19-May 28 May 6 2:00 Gibbous 1P/Halley
Delta Aquarid (S) Jul 21-Aug 23 Jul 30 6:00 First Quarter 96P/Machholz
Perseid (N) Jul 17-Aug 24 Aug 12/13 14:00/2:30 Third Quarter 109P/Swift-Tuttle
Orionid Oct 2-Nov 7 Oct 21 6:00 First Quarter 1P/Halley
Taurids Sep 7-Nov 19

Nov 10/11

Nov 4/5

12:00

Crescent

Full

2P/Encke
Leonid Nov Nov 17 17:00 New 55P/Tempel-Tuttle
Geminid Dec 4-16 Dec 14 6:30 Crescent 3200 Phaethon*
Quadrantid (N) Dec 26-Jan 10 Jan 3 14:00 Full 2003 EH1

S= best viewed from Southern Hemisphere locations

N= best viewed from Northern Hemisphere locations

*This is an asteroid with a weird orbit that takes it very close to the Sun!

 

Here is a list of things you can do to ensure the best meteor viewing experience.

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  • Check the weather. If it’s going to be completely overcast your meteor shower is ruined.
  • Is the Moon up? Is it more than a crescent? If the answer to both of these is yes you will have a more difficult time seeing meteors. The big, bright ones will still shine through but those are rare.
  • When trying to catch a meteor shower, make sure the constellation the shower will radiate from is actually up that night. Hint: Meteor showers are named after the constellation they appear to radiate from.
  • You need the darkest skies possible. So get away from cities and towns. The International Dark Sky Association has a dark sky place finder you can use. Your best bet is to find an empty field far from man-made light pollution.
  • Make sure trees and buildings aren’t obscuring your view.
  • It takes about 30 minutes for your eyes to completely adjust to the darkness. If you have a flashlight, cover it with red photography gel to help keep your eyes adjusted.
  • Ditch the cell phone. Cell phones ruin your night vision. Every time you look at your screen your eyes have to readapt to the dark when you look back up at the sky. There are apps you can download that dim your screen (iPhone, Android) but your eyes will still need time to adjust to the darkness if you glance at your phone. Also looking away almost guarantees the biggest meteor will streak by at just that moment.
  • Dress comfortably. In the fall and winter, wear warm clothes and have hot chocolate and coffee on hand. In the spring and summer, some cool beverages will enhance your experience. Make sure you have blankets to lay on or comfortable chairs so you can keep your eyes on the skies.

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Follow these guidelines and you’ll have the best chance of watching 4.5 billion years of history burn up before your very eyes.

Star Wars Planets: More Science Fact than Fiction

 

By Knicole Colon, PhD

The Star Wars universe is enormous, with hundreds of planets and moons that have a range of properties.  Given that astronomers have now discovered some ~1500 exoplanets along with, of course, the 8 planets and ~150 moons in our Solar System, it should be no surprise that astronomers are discovering more and more real planets that are similar to the fictional planets in the Star Wars universe.

 

First, let us look at Tatooine, the home planet of Anakin and Luke Skywalker.  The most unique feature of this planet is that it orbits around two stars.  In fact, one of the most iconic shots from the Star Wars movies is of Luke on Tatooine with two stars setting in the sky in the background.  Yet, up until a few years ago, astronomers were not sure if planets could actually exist in stable orbits around more than one star.  The Kepler mission changed everything when it discovered a planet orbiting two ordinary stars.  That planet, Kepler-16b, is most likely a gas giant planet that is more similar to Saturn than the rocky/desert planet that Tatooine is, but it is still exciting that planets with multiple stars like Tatooine do exist after all.  Plus, we now understand that there is no reason a planet can’t exist in a stable orbit, even in the habitable zone, around two or more stars.

 

Compared to Tatooine, Kamino is a bit less fantastical.  Kamino is an ocean planet where the clone army was created.  While I can’t speak to whether any clone armies exist somewhere in the real universe, it is a fact that water worlds like Kamino can exist.  GJ 1214b is an exoplanet that is a bit larger than Earth, and for awhile it was believed to be a pure ocean planet based on observations that probed its atmosphere.  It is now believed to have a uniform cloud layer high up in its atmosphere, but it is still possible that underneath that cloud layer, there exists one big ocean.  Maybe it’s even constantly raining there, just like in scenes on Kamino in Episode II!  Even though ocean planets really can exist, I don’t know that anyone would actually want to live on a water world where it’s potentially always raining.

 

If Kamino were further from its star and therefore a lot colder, it might be something like Hoth.  Hoth is (in)famous for being a frigid planet, covered by ice and snow.  During the so-called “polar vortex” this past winter, I recall hearing numerous references of Earth being very much like Hoth.  Since winter did eventually end here and summer is coming (unlike in Game of Thrones), Earth is not a good example of a real Hoth-like planet.  However, there is a growing number of small, potentially rocky exoplanets that orbit at very large distances from their host stars.  Being so far from the main source of heat in a planetary system means that these planets are quite cold, and could very well have Hoth-like climates.  One example is OGLE-2006-BLG-109Lc, which takes about 15 years to orbit its host star.  Based on the temperature of its host star and its orbital distance from its star, that planet has an estimated temperature of -360 degrees Fahrenheit.  I’m thinking that might be a bit too cold for anyone to survive there, so if anyone wanted to visit a “real” Hoth one day, we might need to find a planet that is a bit warmer.  Or, just wait until next winter comes.

 

On the opposite end, a lava planet like Mustafar is not an ideal place to settle down either.  Mustafar is the setting for the epic showdown between Darth Vader, (spoiler alert!) previously known as Anakin Skywalker, and Obi-Wan Kenobi.  In that fight scene, they have to take great care to avoid lava spewing at them.  Interestingly, the volcanic activity on Mustafar is supposed to be a result of the gravitational effect caused by two nearby gas giant planets.  This is very similar to the effect Jupiter has on its moons, in particular Io.  Because of gravitational stresses, Io is the most geologically active object in our Solar System, and images have even been taken of volcanic eruptions on its surface.  There are also known exoplanets that are so hot they probably have lava oceans, thanks to orbiting extremely close to their host stars.  One example is CoRoT-7b, which has an orbital period of just ~ 0.85 days or ~ 20 hours!  This was another discovery not expected by astronomers, simply because it was not believed that a planet could survive being so close to its host star.  While CoRoT-7b will likely be “eaten” by its star eventually, for now it is in a stable orbit, with lava likely flowing happily all over its surface.  For all we know, there is some villainous person like Darth Vader hiding there now, preparing to take over the universe.  We can only hope there is some Jedi-type person who is willing to brave the lava and take the villain down!

 

Last but not certainly not least, we have the Death Star.  Its name is quite misleading, since the Death Star is no star.  And, as Obi-Wan Kenobi also pointed out, “That’s no moon. It’s a space station.”  While the Death Star is a feat of engineering rather than an astronomical object, there was a bit of a ruckus in the astronomical community when pictures of Saturn’s moon Mimas were taken by the Cassini probe in 2005.  That’s because Mimas has a remarkably large crater on its surface, giving it a similar appearance as the Death Star.  Thankfully, the resemblance ends there.  Mimas does not have a powerful superlaser that is capable of destroying an entire planet.  But, if it did have a laser, and if it was used by villains to destroy the Earth, I imagine Earth’s  crumbled remains would eventually form what resembles an asteroid belt.  That is something to keep in mind – for any extrasolar asteroid belts that are discovered, we should consider that they could be the result of destruction by a Death Star.

 

As time goes on and astronomers keep hunting for planets, the fictional Star Wars planets are going to become increasingly realistic.  Still, we will never be able to find the “real” Tatooine or Hoth because those planets existed “a long time ago in a galaxy far, far away….”