Monday, May 31, 2021

An interesting pair

Lately, there have been several missions to Mars; a number more to the Moon and the "rocky" planets in our solar system are planned. Among these, NASA and JPL are working on two missions to Venus, the planet physically very similar to Earth, but, environmentally speaking, very different.

Venus and Earth.
(image credit NASA/JPL)

Venus' orbit is closer to the Sun. It is also the closest planet to us, its distance from the Sun is 72% of Earth's distance. This implies that Venus may have had a climate similar to Earth's in the earlier years of its existence. It makes sense that a closer distance to the Sun would result in a higher, but still tolerable average surface temperature there. Venus orbits within the "Goldilocks" zone, nearer the inner limit. Mars orbits inside the outer limit. Water can exist in a liquid state in that zone. However, at the present time, Venus' surface temperature is about 460[!] degrees Celsius. In addition, the atmospheric pressure is about 90 times that of our home planet; the composition of its atmosphere is also very different from ours. The reason for this extreme climate change is unknown, a greenhouse gas effect, perhaps? The rotational axis of Venus is only 2.3 degrees off its orbital plane and Venus rotates "retrograde" once in 243 days; could this have contributed to the current situation? Finding a possible cause is also a purpose of the two missions. 

As usual, NASA's planned Venus missions are named to have some clever, and purpose-implying acronyms. VERITAS (Venus Emissivity, Radio science, InSAR [Interferometric Synthetic Aperture Radar], Topography, Spectroscopy) will orbit Venus with the purpose of obtaining surface and interior gravitational details. Perhaps there are formations (i.e. possible traces of lake beds or river valleys) that indicate the presence of water at an earlier time. There will also be an effort to determine whether there is evidence of tectonic plates and activity in the past, or even now. 

The other orbiter, DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, Imaging Plus) consists of an orbiter and a lander. The lander is designed to settle on the surface of Venus, to measure atmospheric details on the way down, and surface characteristics as well. Both orbiters will probably act as communications relays. Lately, there have been some reports of detecting phosphine gas in the atmosphere, maybe indicating some form of airborne life. Others disagree. After a number of years of lax interest, Venus has come to the forefront of scientific investigation again.

To withstand the current temperatures on Venus, a lander will have to have especially well designed heat protection. Russia sent the world's first-ever lander to Venus (Venera 9) in 1975; it sent signals for a little more than 50 minutes, after which contact was lost. There have been a number of landers by both Russia and NASA since then. I think that the super-hot environment likely gets the better of most of them.

Venus' atmosphere now is mostly carbon dioxide, with sulfur dioxide clouds and sulfuric-acid rain drops. Life on Earth (you and I are included) also generates carbon dioxide all the time, much of which, via a series of chemical actions, is converted back to oxygen by plankton in the oceans, and our plants and trees. But our industrial and agricultural activities are releasing large amounts of methane (20x more efficient at trapping heat than CO2) and other pollutants, some of which also trap heat. Recent climate changes hint that global warming is happening now. 

Venus and Earth are an interesting, at first glance very similar pair of planets next to each other, yet they have such amazingly different surface environments.

Are we looking at a future on Earth similar to the present conditions on Venus ?  Are we smart and nimble enough to head off such future ?

If you're interested in seeing both of the other two planets sharing the Goldilocks zone, in the western sky on July 12, 2021, around 9:30 pm and later, you can see both Mars and Venus close together (and the Moon a bit farther away). Be careful if you look for Venus before sunset. It is fairly close to the Sun - the standard warning is: don't damage your eyesight, never look at the Sun with the naked eye, binoculars, or telescopes. Proper solar filters are necessary for that. After sunset, Venus, Mars, and the Moon are all close to the West North Western horizon; at that point binoculars are helpful. An unobstructed western horizon is best.





West North West

Simulated image from SkySafari 4 Plus

(References and credits: RASC Observer's Handbook, Scientific American, Wikipedia, NASA/JPL, The Planetary Report)

Friday, April 30, 2021

In thin air


 

In my previous post, I alluded to the immense engineering resources needed for the very demanding, highly successful landing of a very complex rover vehicle (named Perseverance) on Mars.  

The Perseverance rover on Mars had, as part of the payload, a small, specially designed helicopter to test the possibility of flying in the very thin Martian atmosphere. Ingenuity, the name of  this helicopter, has now flown several times on Mars and met and exceeded all goals set for it, including flying far enough to be almost out of sight of the cameras on Perseverance. By necessity, both Perseverance and Ingenuity have to be autonomous; at this time any control signal from Earth would take about 16 and a half minutes to reach both Ingenuity and Perseverance. Information from NASA/JPL regarding Ingenuity says that this little helicopter exceeded the test performance well beyond expectations.

 

(Online readers click on image for larger image)

          This is a picture of Ingenuity flying in the distance (label) imaged from the Perseverance rover (Image from NASA and JPL.) 

NASA News indicates an expanded demonstration phase is going to start a couple of weeks from the time of writing (April 30). Ingenuity has proven that its communications, navigation, imaging and other functions are working well, and expanded operations will be initiated. In future, other Mars helicopters will play an ever-expanding role in getting to know far more Mars details. One of the main efforts is to find out whether traces of past or present extraterrestrial life exist now. There are many interesting topological formations on Mars which may be suitable;  an area on Mars in which traces of life (as we know it) could possibly be found: under the icecaps. Martian seasons are similar to Earth, but last about twice as long. Mars is farther away from the Sun, and takes about twice as much time to complete one orbit. 

Below are some of pictures showing the edges of Martian ice caps. The ice caps contain water ice for the most part and are usually covered by CO2 ice (dry ice) during the Martian "winter". The caps melt and rebuild much like on Earth over the span of the Martian "year". Wikipedia contains details regarding Martian polar ice caps.

 

(Online readers click on image for larger scale)

(Credit for above images: NASA/JPL, Caltech, University of Arizona)

It seems that this rough terrain would be problematic for any rover, but could much more easily be explored by drone-like "Ingenuity" helicopters. 

There is a iGadgetPro YouTube entry showing ice and dust avalanches at the edge of the North Polar ice cap. The images were obtained by NASA's Reconnaissance orbiter's HIRISE camera.




(Online readers click on image for larger scale)

(Credit for above images: NASA/JPL, Caltech, University of Arizona)

When the Sun shines on the layers of the ice caps edges, the warmth makes the ice unstable. Blocks of rock and ice can break off and fall down the about 500m tall edges to create ice and dust clouds when they hit bottom. The colours vary depending on the proportions of dust and ice mixed in these avalanches. 

It always amazes me to see dense clouds of dust in such a thin atmosphere in pictures transmitted from Mars. Well, it made the idea to try flying aircraft on Mars plausible. 



Monday, March 1, 2021

Life on Mars?


The recent landing of the newest Martian Rover (named Perseverance) on February 18, 2021 is truly amazing. The engineering resources deployed to reach this highly difficult goal are overwhelming. Perseverance has as one of its main tasks the finding possible traces of past or present life on Mars. There are several new and proven sensing, imaging, and analyzing devices on board, in addition to others of Mars-proven technologies. Congratulations to everyone who is involved with and contributes to this astounding feat. 

The picture shows a bleak, dry, and waterless landscape, unlikely to be very hospitable to life. But we have images of what appear to be momentary water flows on some Martian crater slopes. We know from past rovers that, in some areas, water ice is present close to the surface. That is a driving reason behind the plans to land people on Mars in future.

Perseverance on Mars (from Space.com)

This landing achievement, the activities planned for this most complex of Martian rovers, and the recent close opposition of Mars in our sky, made me think of a book my mother gave me in 1953, knowing my interest in astronomy. The book's contents address the idea that life of some kind exists everywhere in the universe. Its title is (translated from German) "What lives on the stars"; in it, the author Desiderius Papp describes the intense human fascination with extraterrestrial life during the period in the late 1920s. I had a look into that book again while writing this.

Humanity has for ages "populated" Mars (and the other planets, and some of their moons) with some type of life, usually at least equal, if not superior to us. In the later part of the 1920s a lot of people again speculated about the existence of extraterrestrial life on the planets of our solar system. The beginning of this period seems to have been based on the Mars drawings by the astronomer Giovanni Schiaparelli, who observed Mars for many years in the 1870's and beyond. Some of these drawings show thin lines, which he labelled "canali" (channels), later translated by others as "canals". 

Schiaparelli's visual images were produced using a modest telescope (by today's standards) at an Observatory in northern Italy, working near the limits of its capabilities. As a conscientious observer, he must have had some doubts about the lines he saw, asking himself whether they were optical illusions or real. Many other astronomers of renown never saw these channels. In the 1920's, on and after the 50th anniversary of Schiaparelli's publication of his drawings, the general public got excited over the idea that these supposed canals were the product of highly intelligent and accomplished beings, trying to save their existence by collecting the meltwater from Mars' icecaps; realizing that their planet was rapidly losing its water. 



One of Giovanni Schiaparelli's Mars maps (scienceclarified.com)

It seems that Schiaparelli never promoted those ideas himself (he died in 1910).  However, there were numerous people who expanded this concept, well-known scientists, poets, researchers, and authors of phantasy literature, comics etc., all contributed. One popular astronomer (Camille Flammarion) had no compunctions about stating that these canals were, without a doubt, the result of beings with immensely superior logic and capabilities. Flammarion and other people produced amazingly detailed maps of Mars and the canals, the location of supposedly large cities, possible transportation methods, plant life, many of these ideas amazingly anthropological. One well-known explorer of Mars (Percival Lowell, business man, mathematician, astronomer, author) used his own fortune to build a then state-of-the-art observatory in 1893-1894 at Flagstaff, Arizona, dedicated to the exploration of Mars. He died in 1916, but the Lowell Observatory is still in use today. The observatory's telescope was later used by Asaph Hall, in 1933, to find the then outermost planet in the solar system, Pluto. Hall was also the astronomer who found the two moons of Mars, Phobos and Deimos, in 1877, before the existence of the Lowell Observatory. 

We now know the topology of the Martian surface in reasonable detail. The landscape is indeed complex in many areas, and a number of hints point to the existence of rivers and lakes in the early history of Mars, with canyons and valleys in existence which, however, show no hint of artificial creation. Perhaps Schiaparelli got the first glimpses of something that looked a little like his canali, but we have seen no water canals built by some intelligent and logical beings.

I think that the events referred to above contributed to the path that lead to the efforts referenced at the beginning of this article. We are still looking for life forms that will confirm that we (that is, all life on Earth) are not alone in the universe. From the past and present data sent back by many of the orbiting Mars satellites, on-the-surface moving rovers, and fixed sensing stations, a life as fantasized above is not very likely. At the moment, though, we still cannot answer the questions: is there now or was there ever any life as we know it on Mars? Perhaps any life as we DON'T know it?






 



Sunday, December 27, 2020

A Great "Get-together"

 

One of the rare events in the sky is a conjunction of the two largest planets in our solar system.

I logged into Slooh.com on December 21 to watch their live presentation as this conjunction was in progress. There was also a link to the International Astronomical Center in Abu Dhabi, U.A.E.  The image below originated there; it was shown during the presentation, Saturn at the upper left, Jupiter lower right. 

One day later, the Simon Fraser University's Trottier Observatory did the same thing through its telescope on line, with assistance by the RASC. I also watched that well done presentation via YouTube.

Jupiter/Saturn conjunction (International Astronomical Center)

This conjunction was the result of a particular positioning of Jupiter, Saturn, and Earth in their respective orbits. At the time pictured, the visual separation in the sky of Jupiter and Saturn was about six arc minutes, which is about one fifth of the apparent diameter of our Moon as we see it from Earth. That essentially "united" the two planets into one brighter "star" when looking with our unaided eyes. In reality, Saturn is about 700 million kilometres "behind" Jupiter from Earth's point of view. For perspective, Jupiter is approximately five times Earth's distance from the Sun, Saturn almost twice as far.

The large planets in our solar system orbit the Sun in approximately the same plane; Earth's orbital plane is taken as the reference. As a result, the sun 's annual apparent motion across the sky from Earth appears to be the same from year to year with very small changes over time. This path is called the Ecliptic. The larger planets have orbital planes which are close to the ecliptic, but deviate from it to varying degrees. From our Earth-bound point of view, therefore, for them to appear very close together, such as the Jupiter-Saturn conjunction, happens only now and then. Jupiter can even cover (occult) Saturn, but that is a very rare occurrence. It would require that the centres of Earth, Jupiter, and Saturn be exactly on one specific line. The latest Jupiter-Saturn conjunction came very close to that possibility.

The two planets move quite slowly. Jupiter takes about 3 hours for a distance equal to its own diameter, Saturn is even slower. Both move in the same direction. That means the they will be visible in a pair of binoculars at the same time for a number of days. Standard binoculars have fields of view in the order of 5 to 7 degrees. On January 1, 2021, Saturn and Jupiter are about 2 degrees apart, easily within the same  binocular field of view. Unfortunately they are positioned so close to the sun at this time that they will set closer to sunset every day, so following both planets is going to get more difficult. For this purpose, use your binoculars only after the sun sets. Never look at the sun directly through binoculars, or even with your unprotected eyes only; permanent eye damage may be the result!

Covid-19 is forcing us to keep separate for the time being, it was a good thing to see at least one "heavenly" get-together.
 


Monday, November 30, 2020

An old Workhorse


Since the invention of the telescope and its use for astronomical purposes, the exploration of the universe has progressed at first slowly, and then much faster. That also included advancement in the performance of telescopes themselves. The two main types of telescopes, refractors and reflectors have been around for about 350 years.

Among both types of telescopes, I own one that is my particular favourite. It's a 75mm refractor, purchased used in 1964; its true age I don't know. Here is a picture:


This 75mm, f16 refractor came with a solid wooden equatorial mount tripod (hand-driven tracking). 
The telescope is now mounted on an used EQ5 tripod, purchased about three years ago. 
Right-ascension-tracking and declination motors are powered by a D-battery power pack (not shown).

The telescope has the brand name "Polaris", and someone told me that it is the European version of the "Unitron" brand which was very popular here in North America in the middle of the last century. It has an achromatic objective - chromatic aberration is almost unnoticeable because of the large f-ratio. The telescope produces beautiful views of the major planets, the moon, and open star clusters, but is just on the borderline of dissolving globular clusters into individual stars (i.e. M 13). It's also pretty good at showing the brighter nebulae (Orion nebula, Dumbbell, etc.) and double stars (Mizar, Alcor, the "double double" Epsilon Lyra when pushed to 130 times magnification power, and much more). It's my preferred telescope for Public Astronomy Nights.

In previous centuries, instruments of this size and performance (3", 4", and somewhat larger telescopes) were used to do serious scientific work. For instance, Johann Heinrich von Mädler and Wilhelm Beer produced a highly accurate atlas of the Moon (in four volumes fro 1834 to 1836). It was used by astronomers for over a century.  Mädler  and Beer also produced the first reliable Mars maps and were instrumental (pun intended) in assigning Sinus Meridiani as the Prime Meridian on Mars. Photography was not yet available, so all maps were hand-drawn. Here's an example:  

A part of the "Mappa Selenographica" by Mädler and Beer.

(from planetologia.elte.hu)

Mädler and Beer were also able to determine the rotation period of Mars to within 1.1 seconds. It is highly admirable that astronomers made such demanding observations with telescopes of really moderate size. Even today, refractors built many years ago are still in use for scientific research. 

Photography through my 75mm (3") telescope is also possible. With today's digital cameras and technology it's much easier to take some good pictures. Below is an image of the southern part of the Moon, taken with a handheld Samsung smartphone.  



Handheld smartphone photography through a telescope held against the telescope's eyepiece is difficult, because precisely aligning the optical axes of the smartphone with that of the telescope is mostly a matter of luck. Smartphone holders which attach to a telescope and position the camera lens of a smartphone precisely in line with the telescope eyepiece are available. 

You can see that even old and relatively small telescopes are really useful for getting involved with Astronomy. One additional requirement is a sturdy tripod on which to mount the telescope. It should be included in any telescope purchasing budget. Nothing spoils the performance of telescopes more than a wobbly tripod.

Old workhorses indeed.










Saturday, October 3, 2020

An old Standby

 
In these days of Covid-19, getting together with others to have a look at the night sky is an exercise of don'ts: don't get too close to each other, don't touch or look through the telescope, don't come without a mask, etc. On-line meetings are substituting for the in-person ones. My wife and I are practicing voluntary self-isolation (we are old enough to make this necessary). That means that I'm confined to observing the sky from our home. 
 
We live in a highly light-polluted and horizon-limited area. The smoke from the wildfires in the U.S. has added to the lack of visibility of the stars. There were just a couple of acceptable evenings which led me to look for one of my favorite objects in the sky: The Whirlpool Galaxy not far from the end of the Big Dipper's handle. In a dark sky, M51 can be seen in larger binoculars as a small, diffuse patch of light.

I used my 15x50 Canon stabilized binoculars to try and see it. I did not detect it at all. The gray sky here made it an impossibility.  In earlier years M51 was easy to see from our house; high-rises, new and under construction, now limit our horizon and add much light pollution.

I decided to get my "M51 fix" by posting an image I took a couple of years ago by connecting my computer to Slooh.com to use one of their remotely accessible telescopes and take a picture; below is the result:
 

 Messier 51 
Image taken through the wide-field, 17 inch remote-control Slooh.com telescope located at the Institute of Astrophysics of the Canary Islands. 


 Some history (from Wikipedia):

"What later became known as the Whirlpool Galaxy was discovered on October 13, 1773, by Charles Messier while hunting for objects that could confuse comet hunters, and was designated in Messier's catalogue as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain, although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845, William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m) reflecting telescope at Birr Castle, Ireland, found that the Whirlpool possessed a spiral structure, the first "nebula" to be known to have one. These "spiral nebulae" were not recognized as galaxies until Edwin Hubble was able to observe Cepheid variables in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies even though they are seen close together. The advent of radio astronomy and subsequent radio images of M51 unequivocally demonstrated that the Whirlpool and its companion galaxy are indeed interacting."

There are still some uncertainties regarding M 51. For instance, the distance of it is variously quoted as 31 million light years (NASA), Wikipedia says about 23 million, universetoday.com states 19 to 27 million light years. A location chart is shown above. A dark sky will allow for M 51 to be seen in 10x50 binoculars as a faint patch of light. An 8" (200mm) telescope will begin to show its spiral structure.

Messier 51 is circumpolar, so it is accessible for most of the year. At this time of year, the Big Dipper skirts the northern horizon through the night. M51 is therefore moves along above the northern horizon as well. Give it a try under a dark sky anyway. Its position will improve as we progress through winter and into next year.