APOD: The Day After Mars (2019 Nov 01)

[APOD Robot]

The Day After Mars

Explanation: October 31, 1938 was the day after Martians encountered planet Earth, and everything was calm. Reports of the invasion were revealed to be part of a Halloween radio drama, the now famous broadcast based on H.G. Wells' scifi novel War of the Worlds. On Mars October 20, 2014 was calm too, the day after its close encounter with Comet Siding Spring (C/2013 A1). Not a hoax, this comet really did come within 86,700 miles or so of Mars, about 1/3 the Earth-Moon distance. Earth's spacecraft and rovers in Mars orbit and on the surface reported no ill effects though, and had a ringside seat as a visitor from the outer solar system passed by. Spanning over 2 degrees against stars of the constellation Ophiuchus, this colorful telescopic snapshot captures our view of Mars on the day after. Bluish star 51 Ophiuchi is at the upper right and the comet is just emerging from the Red Planet's bright glare.

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[RocketRon]

Thats ~4000 miles further away than it was last time, in 2014 !! ?

[Ann]

Great APOD! You really could imagine that the comet emerging from the glare of Mars was a spaceship full of evil Martians aiming for the Earth!

Nice colors! Mars is really quite red, and the bluish hue of 51 Ophiuchi is a reasonable match for the star's real color.

Mars looks very bright in this picture. Was Mars actually close to Earth when this picture was taken? Or does Mars look so bright because it was just so much brighter than the tiny little comet?

Ann

[Case]

Mars looks very bright in this picture. Was Mars actually close to Earth when this picture was taken? Or does Mars look so bright because it was just so much brighter than the tiny little comet?

According to Stellarium, Mars was at mag 0.87 and 1.632 AU distance, at that time. Mars can be at mag -2, and as close as 0.37 AU. So, it isn’t particulary bright here.

[Ann]

Mars looks very bright in this picture. Was Mars actually close to Earth when this picture was taken? Or does Mars look so bright because it was just so much brighter than the tiny little comet?

According to Stellarium, Mars was at mag 0.87 and 1.632 AU distance, at that time. Mars can be at mag -2, and as close as 0.37 AU. So, it isn’t particulary bright here.

Thanks, Case!

Ann

[orin stepanek]

Beautiful photo; wish one could have been taken from Mars!

[Chris Peterson]

Mars looks very bright in this picture. Was Mars actually close to Earth when this picture was taken? Or does Mars look so bright because it was just so much brighter than the tiny little comet?

You can't even "see" Mars in this image. Just its light. At the scale of this image, Mars itself is smaller than one pixel. An unresolved point source. And yes, it's extremely bright. 36 times brighter than 51 Oph, 5000 times brighter than the comet. Far more dynamic range than our computer displays can present.

[Trailblazer]

Excellent post today, folks

I was wondering why you didn't mention Orson Welles - He was, after all, the genius behind the 1938 broadcast that created all the panic back then.

[neufer]

I was wondering why you didn't mention Orson Welles -
He was, after all, the genius behind the 1938 broadcast that created all the panic back then.

Click to play embedded YouTube video.

<<Leonhard Euler (15 April 1707 – 18 September 1783) was a Swiss mathematician, physicist, astronomer, geographer, logician and engineer who made important and influential discoveries in many branches of mathematics, such as infinitesimal calculus and graph theory, while also making pioneering contributions to several branches such as topology and analytic number theory. He also introduced much of the modern mathematical terminology and notation, particularly for mathematical analysis, such as the notion of a mathematical function. He is also known for his work in mechanics, fluid dynamics, optics, astronomy and music theory. Euler was one of the most eminent mathematicians of the 18th century and is held to be one of the greatest in history. He is also widely considered to be the most prolific mathematician of all time. His collected works fill 92 volumes, more than anyone else in the field. A statement attributed to Pierre-Simon Laplace expresses Euler's influence on mathematics: "Read Euler, read Euler, he is the master of us all.">>

<<The Bernoulli family of Basel was a patrician family, notable for having produced eight mathematically gifted academics who, among them, contributed substantially to the development of mathematics and physics during the early modern period.>>

[neufer]

<<At the time of discovery C/2013 A1 (Siding Spring) was 7.2 AU from the Sun and located in the constellation Lepus. Comet C/2013 A1 probably took millions of years to come from the Oort cloud. C/2013 A1 passed the planet Mars very closely on 19 October 2014, at a distance of 140,500 km. During the flyby, orbiters around Mars detected thousands of kilograms per hour of comet dust composed of magnesium, iron, sodium, potassium, manganese, nickel, chromium and zinc. In addition, the comet nucleus was determined to be between 400 and 700 meters, much smaller than originally assumed. The nucleus rotates once every eight hours.>>

<<69230 Hermes, provisional designation 1937 UB, is a 810m/540m binary asteroid on an eccentric orbit, classified as a potentially hazardous asteroid and near-Earth object of the Apollo group, that passed Earth at approximately twice the distance of the Moon on 30 October 1937.

Hermes is an Apollo asteroid, a subgroup of near-Earth asteroids that cross the orbit of Earth. It orbits the Sun at a distance of 0.6–2.7 AU once every 2 years and 2 months. Its orbit has an eccentricity of 0.62 and an inclination of 6° with respect to the ecliptic. Due to its eccentricity, Hermes is also a Mars- and Venus-crosser. Frequent close approaches to both Earth and Venus make it unusually challenging to forecast its orbit more than a century in advance, though there is no known impact risk within that timeframe.

The asteroid has an Earth minimum orbital intersection distance of 0.0041 AU (610,000 km) which translates into 1.6 LD. On 30 October 1937, Hermes passed 0.00494 AU (739,000 km) from Earth, and on 26 April 1942, 0.0042415 AU (634,520 km) from Earth. In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7 lunar distances; the second pass was unobserved at the height of the Second World War. For decades, Hermes was known to have made the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach (by 4581 Asclepius) observed. At closest approach, Hermes was moving 5° per hour across the sky and reached 8th magnitude.>>

<<4581 Asclepius (ə-SKLEE-pee-əs) is a ~300 m asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group that makes close orbital passes with Earth.

Asclepius passed by Earth on 22 March 1989, at a distance of 684,000 km. "On the cosmic scale of things, that was a close call," said Dr. Henry Holt. Geophysicists estimate that collision with Asclepius would release energy comparable to the explosion of a 600 megaton atomic bomb. The asteroid was discovered 31 March 1989, nine days after its closest approach to the Earth.>>

[DL MARTIN]

Thanks for animating the event in such an artistic manner. The comet's presence is of heroic stature - one for the gallery.

[Ann]

Click to play embedded YouTube video.

[MarkBour]

What a gorgeous image, today.

A star-spangled image of the comet's course, scarce above the air, next to Mars' bright red glare.
It gives proof that the night sky can yield images quite fair.

(Apologies to Francis Scott Key)

[alter-ego]

Beautiful photo; wish one could have been taken from Mars!

There were, just none as visually stunning as earth-based images. Emily Lakdawalla's post 2 weeks later presents three amateur images (including today's) and mars-base images from rover Curiosity, Mars Reconnaissance Orbiter, MAVEN, Mars Express, and ISRO MOM (later post). Obviously, taking images from the orbiters involved timing and pointing adjustments. Of the (then) 5 orbiters capable of imaging the comet, only 4 were successful. The timings were spread out from minutes to hours before/after closest approach. From an ground-based observer point of view, my favorites are images from the two rovers, Curiosity and Opportunity. Curiosity showed Mar's horizon through a dusty atmosphere in twilight with a faint, point-source comet. Opportunity showed a moving, fuzzy comet trailing in a different direction than the stars.

[neufer]

Mars looks very bright in this picture. Was Mars actually close to Earth when this picture was taken? Or does Mars look so bright because it was just so much brighter than the tiny little comet?

You can't even "see" Mars in this image. Just its light. At the scale of this image, Mars itself is smaller than one pixel. An unresolved point source. And yes, it's extremely bright. 36 times brighter than 51 Oph, 5000 times brighter than the comet. Far more dynamic range than our computer displays can present.

• "Mars itself is smaller than one pixel"

The Comet got as close as 21 Mars diameters away.

(Apologies to Keegan-Michael Key)

[Chris Peterson]

Mars looks very bright in this picture. Was Mars actually close to Earth when this picture was taken? Or does Mars look so bright because it was just so much brighter than the tiny little comet?

You can't even "see" Mars in this image. Just its light. At the scale of this image, Mars itself is smaller than one pixel. An unresolved point source. And yes, it's extremely bright. 36 times brighter than 51 Oph, 5000 times brighter than the comet. Far more dynamic range than our computer displays can present.

• "Mars itself is smaller than one pixel" :?:

The Comet got as close as 21 Mars diameters away.

The pixel scale of this image (the full size click through image) is 7.1 arcseconds/pixel. At the time, Mars subtended 6 arcseconds. So it just fits inside a single pixel.

[neufer]

You can't even "see" Mars in this image. Just its light. At the scale of this image, Mars itself is smaller than one pixel. An unresolved point source. And yes, it's extremely bright. 36 times brighter than 51 Oph, 5000 times brighter than the comet. Far more dynamic range than our computer displays can present.

• "Mars itself is smaller than one pixel"

The Comet got as close as 21 Mars diameters away.

The pixel scale of this image (the full size click through image) is 7.1 arcseconds/pixel. At the time, Mars subtended 6 arcseconds. So it just fits inside a single pixel.

I see... a day after its close approach.

(I would have been out there at Grover's Mill with my pitchfork if I had been alive back then.)

[RocketRon]

If Mars is one pixel, why is the comet so many pixels. ??
That doesn't quite add up..
Even my pocket camera can do better than that.
& surely this is telescopic view ?

All credit to Shirley - and Rolando !

[orin stepanek]

Beautiful photo; wish one could have been taken from Mars!

There were, just none as visually stunning as earth-based images. Emily Lakdawalla's post 2 weeks later presents three amateur images (including today's) and mars-base images from rover Curiosity, Mars Reconnaissance Orbiter, MAVEN, Mars Express, and ISRO MOM (later post). Obviously, taking images from the orbiters involved timing and pointing adjustments. Of the (then) 5 orbiters capable of imaging the comet, only 4 were successful. The timings were spread out from minutes to hours before/after closest approach. From an ground-based observer point of view, my favorites are images from the two rovers, Curiosity and Opportunity. Curiosity showed Mar's horizon through a dusty atmosphere in twilight with a faint, point-source comet. Opportunity showed a moving, fuzzy comet trailing in a different direction than the stars.

Tnx; looks like the mars based cameras were a little bit off!

[Chris Peterson]

If Mars is one pixel, why is the comet so many pixels. ??
That doesn't quite add up..
Even my pocket camera can do better than that.
& surely this is telescopic view ?

As is always the case with an active comet, we can't see the nucleus because it is shrouded in the dust and gas of the coma. The coma of the comet is several times larger than Mars, and the tail is many Mars diameters long. (And yes, it is a telescopic view... what makes you think otherwise?)

[neufer]

Beautiful photo; wish one could have been taken from Mars!

There were, just none as visually stunning as earth-based images. Emily Lakdawalla's post 2 weeks later presents three amateur images (including today's) and mars-base images from rover Curiosity, Mars Reconnaissance Orbiter, MAVEN, Mars Express, and ISRO MOM (later post). Obviously, taking images from the orbiters involved timing and pointing adjustments. Of the (then) 5 orbiters capable of imaging the comet, only 4 were successful. The timings were spread out from minutes to hours before/after closest approach. From an ground-based observer point of view, my favorites are images from the two rovers, Curiosity and Opportunity. Curiosity showed Mar's horizon through a dusty atmosphere in twilight with a faint, point-source comet. Opportunity showed a moving, fuzzy comet trailing in a different direction than the stars.

Tnx; looks like the mars based cameras were a little bit off!

Having to 'Duck and Cover' for both Comet Siding Spring & the Sun probably didn't help the situation.

Mars Orbiters 'Duck and Cover' (Artist's Concept)

---

Mars Orbiters 'Duck and Cover' for Comet Siding Spring Flyby

<<This artist's concept shows NASA's Mars orbiters lining up behind the Red Planet for their "duck and cover" maneuver to shield them from comet dust that may result from the close flyby of comet Siding Spring (C/2013 A1) on Oct. 19, 2014. The comet's nucleus will miss Mars by about 139,500 kilometers, shedding material as it hurtles by at about 56 kilometers per second [~12.6 lunar distances per day], relative to Mars and Mars-orbiting spacecraft. NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data. The NASA orbiters at Mars are Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN.>>

[orin stepanek]

[quote=neufer

Mars Orbiters 'Duck and Cover' (Artist's Concept)

---

Mars Orbiters 'Duck and Cover' for Comet Siding Spring Flyby

<<This artist's concept shows NASA's Mars orbiters lining up behind the Red Planet for their "duck and cover" maneuver to shield them from comet dust that may result from the close flyby of comet Siding Spring (C/2013 A1) on Oct. 19, 2014. The comet's nucleus will miss Mars by about 139,500 kilometers, shedding material as it hurtles by at about 56 kilometers per second [~12.6 lunar distances per day], relative to Mars and Mars-orbiting spacecraft. NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data. The NASA orbiters at Mars are Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN.>>

[/quote]

Yup; that was really close! Maybe Mars could have had a third moon!

[Chris Peterson]

Yup; that was really close! Maybe Mars could have had a third moon! :mrgreen:

No matter how close it came, it could never have been captured. That's the case for all two-body interactions.

[RocketRon]

You'd wonder how all the moons in our Solar System came to be there then ?
Obviously there is some mechanism whereby they can be captured...

[RocketRon]

If my little pocket camera can take an image of Mars that shows (more or less) the
sunlit crescent, and the surrounding starfield are mostly mere pinprick dots, then there
is no way that in the telescopic view here of Mars and comet is Mars merely one pixel ?
That defies common sense even ??? The comet head itself may be a different matter.

Googling for existing earthbound telescopic views of Mars shows quite some detail,
and one pixel they are certainly not. Isn't that how the "canals of Mars" came into
being, with some of the earlier telescopes ?