Artist's impression of the Mars Moons Exploration (MMX) spacecraft. Credit: JAXA
In the coming decades, the world’s largest space agencies hope to mount some exciting missions to the Moon and to Mars. Between NASA, Roscosmos, the European Space Agency (ESA), the Chinese National Space Agency (CNSA) and the Indian Space Research Organization (ISRO), there is simply no shortage of proposals for Lunar bases, crewed missions to Mars, and robotic explorers to both.
However, the Japanese Aerospace Exploration Agency (JAXA) has a different mission in mind when it comes to the coming decades. Instead of exploring the Moon or Mars, they propose exploring the moons of Mars! Known as the Martian Moons Exploration (MMX) mission, the plan is to have a robotic spacecraft fly to Phobos and Deimos to explore their surfaces and return samples to Earth for analysis.
This image taken by the Mars Reconnaissance Orbiter's HiRise camera shows the bright landing platform left behind by NASA's Mars Exploration Rover Opportunity when it landed in 2004. Opportunity landed on the surface of Mars and then bounced and tumbled into the Eagle Crater. The image was taken on April 8, 2017. Image: NASA/JPL-Caltech/Univ. of Arizona
NASA’s eagle-eyed Mars Reconnaissance Orbiter (MRO) has captured orbital images of Opportunity’s Hole-In-One landing site, smack dab in the middle of Eagle Crater on the surface of Mars.
Opportunity arrived at Mars on January 25th, 2005. It’s landing was slowed by parachute, and cushioned by airbags. Once it hit the surface, it bounced its way into “Eagle Crater“, a feature a mere 22 meters across. Not a bad shot!
This is the first color image that the High Resolution Imaging Science Experiment (HiRise) has captured of Opportunity’s landing site. It shows the remarkable landing site inside the crater, where the landing pad was left behind after Opportunity rolled off of it and got going. It also shows the rover’s parachute and backshell.
It’s amazing that, given the relatively smooth surface in Opportunity’s landing area, the rover came to rest inside a small crater. When Opportunity “woke up” at its landing site, its first images were of the inside of Eagle Crater. This was the first look we ever got at the sedimentary rocks on Mars, taken by the rover’s navigation camera.
Opportunity’s navigation camera took this picture, one of the rover’s first, of the inside of Eagle Crater. Exposed Martian rocks are visible. NASA/JPL
After leaving Eagle Crater, Opportunity took a look back and captured a panoramic image. Plainly visible is the rover’s landing pad, the exposed sedimentary rock, and the rover’s tracks in the Martian soil.
This panorama image, called “Lion King” was assembled from 558 images totalling over 75 megabytes. The rock outcrop, the landing pad, and the rover’s tracks are all clearly visible. Image: NASA/JPL/Cornell
MRO arrived at Mars a couple years later, and by that time Opportunity had already left its landing site and made its way south to the much larger Victoria Crater.
When the Mars Reconnaissance Orbiter arrived at Mars, 2 years after Opportunity touched down there, Opportunity had left Eagle Crater and travelled the 6 km to Victoria Crater. By NASA/JPL/University of Arizona – http://photojournal.jpl.nasa.gov/catalog/PIA08813, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4211043
Opportunity is still chugging along, doing valuable work. And so is the MRO and its HiRise instrument. At this point, Opportunity has to be considered one of the most successful scientific undertakings ever.
Special Guest:
This week’s special guest is Brad Peterson. Brad is a returning guest, and since his last appearance, he has been asked by NASA to serve as a community co-chair, with Debra Fischer of Yale, for the Science and Technology Definition Team for the Large Ultraviolet, Optical, and Infrared Surveyor (LUVOIR).
Brad has carried out research on active galactic nuclei for his entire career. He has been developing the technique of reverberation mapping for over 25 years. He is currently on appointment at STScI as Distinguished Visiting Astronomer, after retiring from the faculty of The Ohio State University in 2015 with 35 years of service, the last nine as chair of the Department of Astronomy. He is also a member of the NASA Advisory Council, for which he chairs the Science Committee. He was recently named chair-elect for the Astronomy Section of the AAAS.
We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
Announcements:
On Friday, May 12, the WSH will welcome authors Michael Summers and James Trefil to the show to discuss their new book, Exoplanets: Diamond Worlds, Super Earths, Pulsar Planets and the New Search for Life Beyond Our Solar System. In anticipation of their appearance, the WSH Crew is pleased to offer our viewers a chance to win one of two hard cover copies of Exoplanets. Two winners will be drawn live by @fraser during our show on May 12th. To enter for a chance to win a copy of Exoplanets, send an email to: [email protected] with the Subject: Exoplanets. Be sure to include your name and email address in the body of your message so that we can contact the winners afterward. All entries must be electronically postmarked by 23:59 EST on May 10, 2017, in order to be eligible. No purchase necessary. Two winners will be selected at random from all eligible entries. Good luck!
If you’d like to join Fraser and Paul Matt Sutter on their tour to Iceland in February 2018, you can find the information at astrotouring.com.
If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page<
Approximately every two years, Earth and Mars are at the closest point to each other in their orbits (i.e. opposition). Credit: NASA
As neighboring planets, Earth and Mars have a few things in common. Both are terrestrial in nature (i.e. rocky), both have tilted axes, and both orbit the Sun within its circumstellar habitable zone. And during the course of their orbital periods (i.e. a year), both planets experience variations in temperature and changes in their seasonal weather patterns.
However, owing to their different orbital periods, a year on Mars is significantly longer than a year on Earth – almost twice as long, in fact. And because their orbits are different, the distance between our two planets varies considerably. Basically, every two years Earth and Mars will go from being “at conjunction” (where they are farther from each other) to being “at opposition” (where they are closer to each other).
Orbital Period:
Earth orbits the Sun at an average distance (semi-major axis) of 149,598,023 km (92,955,902 mi; or 1 AU), ranging from 147,095,000 km (91,401,000 mi) at perihelion to 152,100,000 km (94,500,000 mi) at aphelion. At this distance, and with an orbital velocity of 29.78 km/s (18.5 mi/s) the time it take for the planet to complete a single orbit of the Sun (i.e. orbital period) is equal to about 365.25 days.
A top-down image of the orbits of Earth and Mars. Credit: NASA
Mars, meanwhile, orbits the Sun at an average distance of 227,939,200 km (141,634,850 mi; or 1.523679 AU), ranging from 206,700,000 km (128,437,425 mi) at perihelion to 249,200,000 km (154,845,700 mi) at aphelion. Given this difference in distance, Mars orbits the Sun at a slower speed (24.077 km/s; 14.96 mi/s) and takes about 687 Earth days (or 668.59 Mars sols) to complete a single orbit.
In other words, a Martian year is almost 700 days long, which works out to being 1.88 times as long as a year on Earth. This means that every time Mars completes a single orbit around the Sun, the Earth has gone around almost twice. During the moments when they are on opposite sides of the Sun, this is known as a “conjunction”. When they are on the same side of the Sun, they are at “opposition”.
Mars Opposition:
By definition, a “Mars opposition” occurs when planet Earth passes in between the Sun and planet Mars. The term refers to the fact that Mars and the Sun appear on opposite sides of the sky. Because of their orbits, Mars oppositions happens about every 2 years and 2 months – 779.94 Earth days to be precise. From our perspective here on Earth, Mars appears to be rising in the east just as the Sun sets in the west.
About every two years, the Earth passes Mars as they orbit around the Sun. Credit: NASA
After staying up in the sky for the entire night, Mars then sets in the west just as the Sun begins to rise in the east. During an opposition, Mars becomes one of the brightest objects in the night sky, and is easy to see with the naked eye. Through small telescopes, it will appear as a large and bright object. Through larger telescopes, Mars’ surface features will even become apparent, which would include its polar ice caps.
An opposition can also occur anywhere along Mars’ orbit. However, opposition does not necessary mean that the two planets are at their closest overall. In truth, it just means that they are are at their closest point to each other within their current orbital period. If Earth and Mars’ orbits were perfectly circular, they would be closest to each other whenever they were at opposition.
Instead, their orbits are elliptical, and Mars’ orbit is more elliptical than Earth’s – which means the difference between their respective perihelion and aphelion is greater. Gravitational tugging from other planets constantly changes the shape of our orbits too – with Jupiter pulling on Mars and Venus and Mercury affecting Earth.
Color composite of Mars from seven of its previous oppositions, taken with the Hubble Space Telescope. Credit: NASA/ESA/HST
Lastly, Earth and Mars do not orbit the Sun on the exact same plane – i.e. their orbits are slightly tilted relative to each other. Because of this, Mars and Earth become closest to each other only over the long-term. For instance, every 15 or 17 years, an opposition will occur within a few weeks of Mars’ perihelion. When it happens while the Mars is closest to the sun (called “perihelic opposition”), Mars and Earth get particularly close.
And yet, the closest approaches between the two planets only take place over the course of centuries, and some are always closer than others. To make matters even more confusing, over the past few centuries, Mars’ orbit has been getting more and more elongated, carrying the planet even nearer to the Sun at perihelion and even farther away at aphelion. So future perihelic oppositions will bring Earth and Mars even closer.
On August 28th, 2003, astronomers estimated that Earth and Mars were just 55,758,118 km (34,646,488 mi; 0.37272 AU) apart. This was the closest the two planets had come to each other in almost 60,000 years. This record will stand until August 28th, 2287, at which point the planets will be an estimated 55,688,405 km (34,603,170.6 mi; 0.372254 AU) from each other.
Future Oppositions:
Want to organize your schedule for the next time Mars will be close to Earth? Here are some upcoming dates, covering the next few decades. Plan accordingly!
July 27th, 2018
October 13th, 2020
December 8th, 2022
January 16th, 2025
February 19th, 2027
Mar 25th, 2029
May 4th, 2031
June 27th, 2033
September 15th, 2035
November 19th, 2037
January 2nd, 2040
February 6th, 2042
March 11th, 2044
April 17th, 2046
June 3rd, 2048
August 14th, 2050
And in case your interested, Mars will be making close approaches on two occasions this century. The first will take place on August 14th, 2050, when Mars and Earth will be 55.957 million km (34.77 million mi; or 0.374051 AU) apart; and on September 1st, 2082, when they will be 55,883,780 km (34,724,571 mi; 0.373564 AU) apart.
There’s a reason missions to Mars depart from Earth every two years. Seeking to take advantage of shorter travel times, rovers, orbiters and landers are launched to coincide with Mars being at opposition. And when it comes time to send crewed mission to Mars (or even settlers) the same timing will apply!
A new study led by researchers from OU indicates that the outer planets could be why Mars is significantly smaller than Earth. Credit: NASA
Trojan asteroids are a fascinating thing. Whereas the most widely known are those that orbit Jupiter (around its L4 and L5 Lagrange Points), Venus, Earth, Mars, Uranus and Neptune have populations of these asteroids as well. Naturally, these rocky objects are a focal point for a lot of scientific research, since they can tell us much about the formation and early history of the Solar System.
And now, thanks to an international team of astronomers, it has been determined that the Trojan asteroids that orbit Mars are likely the remains of a mini-planet that was destroyed by a collision billions of years ago. Their findings are detailed in a paper that will be published in The Monthly Notices of the Royal Astronomical Society later this month.
For the sake of their study, the team – which was led by Galin Borisov and Apostolos Christou of the Armagh Observatory and Planetarium in Northern Ireland, examined the composition of Marian Trojans. This consisted of using spectral data obtained by the XSHOOTER spectrograph on the Very Large Telescope (VLT) and photometric data from the National Astronomical Observatory‘s two-meter telescope, and the William Herschel Telescope.
Diagram of Jupiter and the inner Solar System, showing the Jupiter and Martian Trojans (light green) and the Main Belt (teal). Credit: Wikipedia Commons/AndrewBuck
Specifically, they examined two members of the Eureka family – a group of Martian Trojans located at the planet’s L5 point. It is here that eight of Mars’ nine known Trojans exist in stable orbits (the other being at L4), and which are named after the first Martian Trojan ever discovered – 5261 Eureka. Like all Trojans, the Eurekas are thought to have orbited Mars ever since the formation of the Solar System.
In fact, astronomers have suspected for some time that the Martian Trojans could be the survivors of an early generation of planetesimals from which the inner Solar System formed. As Dr. Christou told Universe Today via email:
“[The Trojan family] is unique in the Solar System, in more ways than one. Unlike every other family that exists in the Main Asteroid Belt between Mars and Jupiter, it is made up of olivine-rich asteroids. Also, the asteroids are < 2km across, much smaller than we can see at other families, basically because they are much closer to the Earth than other asteroids. Finally, it is the closest family we know to the Sun, and this has implications on how it formed in that the tiny but continuous action of sunlight may have played a role.”
After combining spectrographic and photometric data on these asteroids, the team found that they were rich in the mineral olivine – a magnesium iron silicate that is a primary component of the Earth’s mantle and (it is believed) other terrestrial planets. This was unusual find as far as asteroids go, but it was even more interesting when compared to 5261 Eureka itself – which also has an olivine-rich composition.
The first X-ray view of Martian soil by Curiosity rover at the “Rocknest” (October 17, 2012), showing traces of feldspar, pyroxenes, and olivine. Credit: NASA/JPL-Caltech/Ames
Given that the Eureka asteroids also have similar orbits, the team concluded that every member of this family is likely to have a common composition – and hence, a common origin. These findings could have drastic implications for both the origin of Martian Trojans, and the origin of the inner Solar System. As Dr. Christou explained:
“The presence of asteroids with exposed olivine on their surfaces constrains the sequence of events that led to Mars’ formation. Olivine forms within objects that grew large enough to differentiate into a crust, mantle and core. Therefore, these objects must have formed before Mars did and were available to participate in Mars’ formation. To expose the olivine, it is necessary to break these objects up through collisions. Our ongoing work indicates that this is unlikely to have happened after the Solar System settled down in its current configuration, therefore there must have been period of intense collisional evolution during the planet formation process.”
In other words, if Mars formed from several types of material that was mixed together, these asteroids would be samples of the original source – i.e. planetesimals. By examining these asteroids further, scientists will be able to learn more about the process through which Mars came to be and (as Christou says) help us “unscramble the Martian omelette.”
This research is also likely to reveal much about the formation of Earth and the other terrestrial planets of the Solar System. Similar efforts will be made with NASA’s upcoming Lucy mission, which is scheduled to launch in October of 2021. Between 2027 and 2033, this probe will study Jupiter’s Trojan population, obtaining information on six of the asteroid’s geology, surface features, compositions, masses and densities to learn more about their origins.
Special Guest:
This week’s special guests are Timothy Spuck, Kathryn Meredith, Dr. James Hammerman and Andreas Stefik of the Innovators Developing Accessible Tools for Astronomy (IDATA) Project Team. The IDATA project aims to design and develop Afterglow Access, a new software tool that will expand accessibility beyond touch, making the universe more accessible to those with visual impairments.
Yerkes Outreach website
Tim Spuck (email: [email protected]) (Associated Universities Inc. STEM Education Development Officer and IDATA PI) currently serves as PI on three NSF supported programs including, Innovators Developing Accessible Tools for Astronomy, the Chile-US Astronomy Education Outreach Summit, and the Astronomy in Chile Educator Ambassadors Program. Tim also remains active within the amateur astronomy community, has directed numerous outreach efforts, and led several small-scale observatory design and construction projects. He earned his Masters degree in Science Education from Clarion University or PA, and is completing his Ed.D. in Curriculum & Instruction at West Virginia University.
Kate Meredith (Yerkes Observatory – University of Chicago, Director of Education Outreach, and IDATA Project Educator) has engaged in curriculum development and project management for the Zooniverse, the Sloan Digital Sky Survey, the Lawrence Hall of Science, the Adler Planetarium Space and Science Museum, and Skynet Junior Scholars (University of Chicago Yerkes Observatory). Kate is passionate about programs that bring authentic research science to learners of all ages, languages, and abilities. As Education Lead on the IDATA project, Kate looks forward to being part of the team that takes accessibility to the next level by creating vision-neutral data acquisition and analysis tools as well as the instructional materials needed to teach new users how to use and apply those tools.
Dr. James K. L. Hammerman (TERC, Co-Director of SEEC and Senior Researcher and Evaluator, IDATA Co-PI) currently leads external evaluations for several projects, including an immersive computer environment for conducting experiments to explore causality and ecology, a state-wide initiative to engage rural youth in computing through programming an online game, and an effort to improve pedagogy among university STEM faculty. Jim has designed, implemented, and researched mathematics and science education curricula and professional development programs, as well as technology tools that support inquiry-oriented learning. Jim is especially interested in adult developmental differences in professional development, data and statistics learning, online and software tools that support exploration, and supporting deeper learning and more reflective practice in professional communities.
Andreas Stefik (University of Nevada – Las Vegas, Assistant Professor of Computer Science and IDATA Co-PI) – For the last decade, Dr. Stefik has been creating technologies that make it easier for people, including those with disabilities, to write computer software. With grants from the National Science Foundation, he helped establish the first national educational infrastructure for blind or visually impaired students to learn computer science. He is the inventor of Quorum, the first evidence-oriented programming language. As part of his work, he is a PI on the NSF-funded AccessCS10K grant that is helping CS 10K projects prepare K-12 teachers to be more inclusive in their computing courses with students with disabilities. Most recently, Dr. Stefik was honored with the 2016 White House Champions of Change award in computer science education.
We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
If you’d like to join Fraser and Paul Matt Sutter on their tour to Iceland in February 2018, you can find the information at astrotouring.com.
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page
This image is a mosaic of all the images captured by the Context Camera (CTX) on NASA's Mars Reconnaissance Orbiter. The CTX has imaged over 99% of the Martian surface. Image: NASA/JPL-Caltech/MSSS
Most of us never do one thing 50,000 times in our life. So for NASA’s Mars Reconnaissance Orbiter (MRO), completing 50,000 orbits around the red planet is a big deal. And, it only took 10 years to do so.
The MRO could be called one of NASA’s flagship missions. It’s presence in orbit around Mars has helped open up our understanding of that planet immensely. And it’s done so while providing us a steady stream of eye candy.
This recent image from MRO’s HiRise camera shows dune structure inside an impact crater. Image: NASA/JPL/University of Arizona
MRO was launched in 2005 and reached Mars orbit in March, 2006. After 10 years at work, it has accomplished a lot. In a recent press release, NASA calls the MRO “the most data-productive spacecraft yet.” Though most of us might know the orbiter because of it’s camera, the High-Resolution Imaging Science Experiment (HiRise), the MRO actually has a handful of other instruments that help the orbiter achieve its objectives. In broad terms, those objectives are:
to study the history of water on Mars
to look at small scale features on the surface, and identify landing sites for future Mars missions
to act as a communications relay between Mars and Earth
MRO investigating Martian water cycle – This artist’s concept represents the “Follow the Water” theme of NASA’s Mars Reconnaissance Orbiter mission. The orbiter’s science instruments monitor the present water cycle in the Mars atmosphere and the associated deposition and sublimation of water ice on the surface, while probing the subsurface to see how deep the water-ice reservoir extends. Image: By NASA/JPL/Corby Waste – http://photojournal.jpl.nasa.gov/catalog/PIA07241 (image link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=374810 (Larger image here.
MRO’s HiRise camera gets all the glory, but it’s another onboard camera, the Context Camera (CTX), that is the real workhorse. The CTX is a much lower resolution than the HiRise, but its file sizes are much more manageable, an important consideration when every file has to travel from Mars to Earth—an average distance of about 225 million km.
CTX has captured 90,000 images so far in MRO’s mission, and each one captures details smaller than a tennis court. In the course of the mission so far, CTX has images that cover 99.1% of the Martian surface. Over 60% of the planet has been covered twice.
“Reaching 99.1-percent coverage has been tricky…” – Context Camera Team Leader Michael Malin
“Reaching 99.1-percent coverage has been tricky because a number of factors, including weather conditions, coordination with other instruments, downlink limitations, and orbital constraints, tend to limit where we can image and when,” said Context Camera Team Leader Michael Malin of Malin Space Science Systems, San Diego.
Malin said, “Single coverage provides a baseline we can use for comparison with future observations, as we look for changes. Re-imaging areas serves two functions: looking for changes and acquiring stereoscopic views from which we can make topographic maps.”
Because the CTX captures image of the same surface areas twice, it documents changes on the surface. There have been over 200 instances of impact craters appearing in a second image of the same area. Scientists have used this to calculate the rate that meteorites impact Mars.
The instruments on board the MRO work as a team. The CTX can capture images of areas of interest, and the HiRise can be used for higher-resolution images of the same area. By locating fresh impact craters, then studying them more closely, the MRO has helped discover the presence of what looked like sub-surface ice on Mars. A third instrument, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), confirmed the presence of ice.
The CTX is the workhorse camera, and the HiRise is the diva, but MRO actually has a third camera: the Mars Color Imager (MARCI). MARCI is a very low resolution camera compared to the others. It’s also a wide-angle camera with really only one purpose: characterizing Martian weather. Every day, MARCI takes about 84 images which together create a daily global map of Mars. You can see a weekly Martian weather report from MARCI here.
The MRO recently manoeuvered itself into position for its next task—helping the InSight Lander. The MRO must receive critical radio transmissions from NASA’s InSight Lander as it descends to Mars. Insight will use its instruments to examine the interior of Mars for clues to how rocky planets form. Not only did MRO help find a landing spot for Insight, but it will hold the lander’s hand as it descends, and it will act as a data relay.
“After 11 and a half years in flight, the spacecraft is healthy and remains fully functional.” – MRO Project Manager Dan Johnston.
There’s no end in sight for the MRO. It just keeps going and going, and fulfilling its mission objectives on a continuing basis. “After 11 and a half years in flight, the spacecraft is healthy and remains fully functional,” said MRO Project Manager Dan Johnston at NASA’s Jet Propulsion Laboratory, Pasadena, California. “It’s a marvelous vehicle that we expect will serve the Mars Exploration Program and Mars science for many more years to come.”
Mercury requests the company of your gaze now through the beginning of April, when it shines near Mars low in the west after sunset. Created with Stellarium
March has been a busy month for planet and comet watchers. Lots of action. Venus, the planet that’s captured our attention at dusk in the west for months, is in inferior conjunction with the Sun today. Watch for it to rise before the Sun in the eastern sky at dawn in about a week.
Mercury like Venus and the Moon shows phases when viewed through a telescope. Right now, the planet is in waning gibbous phase. Stellarium
As Venus flees the evening scene, steadfast Mars and a new planet, Mercury keep things lively. For northern hemisphere skywatchers, this is Mercury’s best dusk apparition of the year. If you’d like to make its acquaintance, this week and next are best. And it’s so easy! Just find a spot with a wide open view of the western horizon, bring a pair of binoculars for backup and wait for a clear evening.
Plan to watch starting about 40 minutes after sundown. From most locations, Mercury will appear about 10° or one fist held at arm’s length above the horizon a little bit north of due west. Shining around magnitude +0, it will be the only “star” in that part of the sky. Mars is nearby but much fainter at magnitude +1.5. You’ll have to wait at least an hour after sunset to spot it.
Have a telescope? Check out the planet using a magnification around 50x or higher. You’ll see that it looks like a Mini-Me version of the Moon. Mercury is brightest when closest to full. Over the next few weeks, it will wane to a crescent while increasing in apparent size.
If you have any difficulty finding brilliant Jupiter and its current pal, Spica, just start with the Big Dipper, now high in the northeastern sky at nightfall. Use the Dipper’s handle to “arc to Arcturus” and then “jump to Jupiter.” Credit: Bob King
If you like planets, don’t forget the combo of Jupiter and Spica at the opposite end of the sky. Jupiter climbs out of bed and over the southeastern horizon about 9 p.m. local time in late March, but to see it and Spica, Virgo’s brightest star, give it an hour and look again at 10 p.m. or later. Quite the duo!
You’re not afraid of getting up with the first robins are you? If you set your alarm to a half hour or so before the first hint of dawn’s light and find a location with an open view of the southeastern horizon, you might be first in your neighborhood to spot Terry Lovejoy’s brand new comet. His sixth, the Australian amateur discovered C/2017 E4 Lovejoyon the morning of March 10th in the constellation Sagittarius at about 12th magnitude.
C/2017 E4 Lovejoy glows blue-green this morning March 26. Structure around the nucleus including a small jet is visible. The comet is currently in Aquarius and quickly moving north and will reach perihelion on April 23. Credit: Terry Lovejoy
The comet has rapidly brightened since then and is now a small, moderately condensed fuzzball of magnitude +9, bright enough to spot in a 6-inch or larger telescope. Some observers have even picked it up in large binoculars. Lovejoy’s comet should brighten by at least another magnitude in the coming weeks, putting it within 10 x 50 binocular range.
This map shows the sky tomorrow morning before dawn from the central U.S. (latitude about 41° north). Created with Stellarium
Good news. E4 Lovejoy is moving north rapidly and is now visible about a dozen degrees high in Aquarius just before the start of dawn. I’ll be out the next clear morning, eyepiece to eye, to welcome this new fuzzball from beyond Neptune to my front yard. The map above shows the eastern sky near dawn and a general location of the comet. Use the more detailed map below to pinpoint it in your binoculars and telescope.
This chart shows the comet’s position nightly (5:30 a.m. CDT) through April 9. On the morning of April 1 it passes just a few degrees below the bright globular cluster M15. Click to enlarge, save and then print out for use at the telescope. Map: Bob King, Source: Chris Marriott’s SkyMap
Spring brings with it a new spirit and the opportunity to get out at night free of the bite of mosquitos or cold. Clear skies!
Mars, as photographed with the Mars Global Surveyor, is identified with the Roman god of war. Credit: NASA
This week, from March 20th to 24th, the 48th Lunar and Planetary Science Conference will be taking place in The Woodlands, Texas. Every year, this conference brings together international specialists in the fields of geology, geochemistry, geophysics, and astronomy to present the latest findings in planetary science. One of the highlights of the conference so far has been a presentation about Mars’ weather patterns.
When it comes to cloud formations, gravity waves are the result of gravity trying to restore them to their natural equilibrium. And while common on Earth, such formation were not thought to be possible around Mars’ equatorial band, where the gravity waves were seen. All of this was made possible thanks to Curiosity’s advantageous position inside the Gale Crater.
Panoramic image showing cirrus clouds in the Martian atmosphere, taken by the Opportunity rover in 2006. Credit: NASA/JPL/Cornell/M. Howard, T. Öner, D, Bouic & M. Di Lorenzo
Located near Mars’ equator, Curiosity has managed to consistently record what is known as the Aphelion Cloud Belt (ACB). As the name would suggest, this annually-recurring phenomena appears during the aphelion season on Mars (when it is farthest from the Sun) between the latitudes of 10°S and 30°N. During aphelion, the point farthest from the Sun, the planet is dominated by two cloud systems.
These include the aforementioned ACB, and the polar phenomena known as Polar Hood Clouds (PHCs). Whereas PHCs are characterized by clouds of carbon dioxide, clouds that form around Mars’ equatorial band are made up water-ice. These cloud systems them dissipate as Mars gets closer to the Sun (perihelion), where increases in temperature lead to the creation of dust storms that limit cloud formation.
During the nearly five years that Curiosity has been operational, the rover has recorded over 500 movies of the equatorial Martian sky. These movies have taken the form of both Zenith Movies (ZMs) – which involve the camera being pointed vertically – and Supra-Horizon Movies (SHM), which were aimed at a lower angle of elevation to keep the horizon in frame.
Using Curiosity’s navigation camera, Jacob Kloos and Dr. John Moores – two researchers from CRESS – made eight recordings of the ACB over the course of two Martian years – specifically between Mars Years 31 and Mars Years 33 (ca. 2012 to 2016). By comparing ZM and SHM movies, they were able to discern changes in the clouds that were both diurnal (daily) and annual in nature.
What they found was that between 2015 and 2016, Mars’ ACB underwent changes in opacity (aka. changes in density) during its diurnal cycle. After periods of enhanced early morning activity, the clouds would reach a minimum by late morning. This is followed by a second, lower peak in the late afternoon, which indicated that Mars’ early morning hours are the most favorable time for the formation of thicker clouds.
Hubble images show cloud formations (left) and the effects of a global dust storm on Mars. Credit: NASA/James Bell (Cornell Univ.), Michael Wolff (Space Science Inst.), and Hubble Heritage Team (STScI/AURA)
As for inter-annual variability, they found that between 2012 and 2016, when Mars moved away from aphelion, there was a corresponding 38% increase in the number of higher-opacity clouds. However, believing these results to be the result of a statistical bias caused by an uneven distribution of videos, they concluded that the difference in opacity was more along the lines of about 5%.
These variations were all of this is consistent with tidal temperature variations, where cooler daytime or seasonal temperatures result in greater levels of condensation in the air. The trend of increasing clouds throughout the day was unexpected, however, as higher temperatures should lead to a decrease in saturation. However, as they explained during their presentation, this too could be attributed to daily changes:
“One explanation for the afternoon enhancement put forth by Tamppari et. al. is that as atmospheric temperatures increase the throughout the day, enhanced convection lifts water vapor to the saturation altitude, therefore increasing the likelihood of cloud formation. In addition to water vapor, dust could also be lifted, which act as condensation nuclei, allowing for more efficient cloud formation.”
However, what was most interesting was the fact that during one of day of observation – Sol 1302, or April 5th, 2016 – the team managed to observe something surprising. When looking at the horizon during an SHM, the NavCam caught sight of parallel rows of clouds which all pointed in the same direction. While such ripples are known to happen in the polar regions (where PHCs are concerned), spotting them over the equator was unexpected.
Sunset photographed from Gale Crater by the Mars Curiosity rover on April 15, 2015 taken using the left eye of the rover’s Mastcam. Credit: NASA/JPL-Caltec
But as Moore explained in an interview with Science Magazine,seeing an Earth-like phenomenon on Mars is consistent with what we’ve seen so far from Mars. “The Martian environment is the exotic wrapped in the familiar,” he said. “The sunsets are blue, the dust devils enormous, the snowfall more like diamond dust, and the clouds are thinner than what we see on the Earth.”
At present, it is not clear which mechanism could be responsible for creating these ripples in the first place. On Earth, they are caused by disturbances below in the troposphere, solar radiation, or jet stream sheer. Knowing what could account for them on Mars will likely reveal some interesting things about its atmosphere’s dynamics. At the same time, further research is necessary before scientists can say definitely that gravity waves were observed here.
But in the meantime, these findings are fascinating, and are sure to help advance our knowledge of the Red Planet’s atmosphere and the water cycle on Mars. As ongoing research has shown, Mars still experiences flows of liquid salt water on its surface, and even experiences limited precipitation. And in telling us more about Mars’ present-day meteorology, it could also reveal things about the planet’s watery past.
To see the recordings of Martian clouds, click here,here and here.
Image taken by the Mars Hand Lens Imager (MAHLI) of Curiosity's wheels on March 19, 2017. Credit: NASA
Since it landed on August 6th, 2012, the Curiosityrover has spent a total of 1644 Sols (or 1689 Earth days) on Mars. And as of March 2017, it has traveled almost 16 km (~10 mi) across the planet and climbed almost a fifth of a kilometer (0.124 mi) uphill. Spending that kind of time on another planet, and traveling that kind of distance, can certainly lead to its share of wear of tear on a vehicle.
That was the conclusion when the Curiosity science team conducted a routine check of the rover’s wheels on Sunday, March 19th, 2017. After examining images taken by the Mars Hand Lens Imager (MAHLI), they noticed two small breaks in the raised treads on the rover’s left middle wheel. These breaks appeared to have happened since late January, when the last routine check of the wheels took place.
To get around, the Curiosity rover relies on six solid aluminum wheels that are 40 cm (16 in) wide. The skin of the wheels is thinner than a US dime, but each contains 19 zigzag-shaped treads that are about 0.75 cm (three-quarters of an inch) thick. These “grousers”, as they are called, bear most of the rover’s weight and provide most of the wheel’s traction.
Close-up image of the broken grousers on Curiosity’s left-middle wheel. Credit: NASA/JPL-Caltech/MSSS
Ever since the rover was forced to cross a stretch of terrain that was studded with sharp rocks in 2013, the Curiosity team has made regular checks on the rover’s wheels using the MAHLI camera. At the time, the rover was moving from the Bradbury Landing site (where it landed in 2012) to the base of Mount Sharp, and traversing this terrain caused holes and dents in the wheels to grow significantly.
However, members of Curiosity’s science team emphasized that this is nothing to be worried about, as it will not affect the rover’s performance or lifespan. As Jim Erickson, the Curiosity Project Manager at NASA’s Jet Propulsion Laboratory, said in a recent NASA press statement:
“All six wheels have more than enough working lifespan remaining to get the vehicle to all destinations planned for the mission. While not unexpected, this damage is the first sign that the left middle wheel is nearing a wheel-wear milestone.”
In addition to regular monitoring, a wheel-longevity testing program was started on Earth in 2013 using identical aluminum wheels. These tests showed that once a wheel got to the point where three of its grousers were broken, it had passed about 60% of its lifespan. However, Curiosity has already driven more than 60% of the total distance needed for it to make it to all of its scientific destinations.
Graphic depicting aspects of the driving distance, elevation, geological units and time intervals of NASA’s Curiosity Mars rover mission, as of late 2016. Credit: NASA/JPL-Caltech
“This is an expected part of the life cycle of the wheels and at this point does not change our current science plans or diminish our chances of studying key transitions in mineralogy higher on Mount Sharp.”
At present, Curiosity is examining sand dunes in the geographical region known as the Murray Buttes formation, which is located on the slope of Mount Sharp. Once finished, it will proceed up higher to a feature known as “Vera Rubin Ridge”, inspecting a layer that is rich in the mineral hematite. From there, it will proceeded to even higher elevations to inspect layers that contain clays and sulfates.
Getting to the farthest destination (the sulfate unit) will require another 6 km (3.7 mi) of uphill driving. However, this is a short distance compared to the kind of driving the rover has already performed. Moreover, the science team has spent the past four years implementing various methods designed to avoid embedded rocks and other potentially hazardous terrain features.
MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity. Credits: NASA/JPL, illustration, T.Reyes
It is expected that this drive up Mount Sharp will yield some impressive scientific finds. During its first year on Mars, Curiosity succeeded in gathering evidence in the Gale Crater that showed how Mars once had conditions favorable to life. This included ample evidence of liquid water, all the chemical elements needed for life, and even a chemical source of energy.
By scaling Mount Sharp and examining the layers that were deposited over the course of billions of years, Curiosity is able to examine a living geological record of how the planet has evolved since then. Luckily, the rover’s wheels seem to have more than enough life to make these and (most likely) other scientific finds.
