Hubble sees martian moon orbiting the Red Planet

July 20, 2017, NASA's Goddard Space Flight Center
Over the course of 22 minutes, Hubble took 13 separate exposures, allowing astronomers to create a time-lapse image showing the tiny moon Phobos during its orbital trek (white dots) around Mars. This image is a composite of separate exposures acquired by NASA's Hubble WFC3/UVIS instrument. Credit: Over the course of 22 minutes, Hubble took 13 separate exposures, allowing astronomers to create a time-lapse image showing the tiny moon Phobos during its orbital trek (white dots) around Mars. This image is a composite of separate exposures acquired by NASA's Hubble WFC3/UVIS instrument.

The sharp eye of NASA's Hubble Space Telescope has captured the tiny moon Phobos during its orbital trek around Mars. Because the moon is so small, it appears star-like in the Hubble pictures.

Over the course of 22 minutes, Hubble took 13 separate exposures, allowing astronomers to create a time-lapse video showing the diminutive moon's orbital path. The Hubble observations were intended to photograph Mars, and the moon's cameo appearance was a bonus.

A football-shaped object just 16.5 miles by 13.5 miles by 11 miles, Phobos is one of the smallest moons in the solar system. It is so tiny that it would fit comfortably inside the Washington, D.C. Beltway.

The little moon completes an orbit in just 7 hours and 39 minutes, which is faster than Mars rotates. Rising in the Martian west, it runs three laps around the Red Planet in the course of one Martian day, which is about 24 hours and 40 minutes. It is the only natural satellite in the solar system that circles its planet in a time shorter than the parent planet's day.

About two weeks after the Apollo 11 manned lunar landing on July 20, 1969, NASA's Mariner 7 flew by the Red Planet and took the first crude close-up snapshot of Phobos. On July 20, 1976 NASA's Viking 1 lander touched down on the Martian surface. A year later, its parent craft, the Viking 1 orbiter, took the first detailed photograph of Phobos, revealing a gaping crater from an impact that nearly shattered the moon.

?Phobos was discovered by Asaph Hall on August 17, 1877 at the U.S. Naval Observatory in Washington, D.C., six days after he found the smaller, outer moon, named Deimos. Hall was deliberately searching for Martian moons.

Both moons are named after the sons of Ares, the Greek god of war, who was known as Mars in Roman mythology. Phobos (panic or fear) and Deimos (terror or dread) accompanied their father into battle.

When the Hubble Space Telescope observed Mars near opposition in May, 2016, a sneaky companion photobombed the picture. Phobos, the Greek personification of fear, is one of two tiny moons orbiting Mars. In 13 exposures over 22 minutes, Hubble captured a timelapse of Phobos moving through its 7-hour 39-minute orbit. Credit: NASA's Goddard Space Flight Center

Close-up photos from Mars-orbiting spacecraft reveal that Phobos is apparently being torn apart by the gravitational pull of Mars. The moon is marred by long, shallow grooves that are probably caused by tidal interactions with its parent planet. Phobos draws nearer to Mars by about 6.5 feet every hundred years. Scientists predict that within 30 to 50 million years, it either will crash into the Red Planet or be torn to pieces and scattered as a ring around Mars.

Orbiting 3,700 miles above the Martian surface, Phobos is closer to its parent planet than any other moon in the solar system. Despite its proximity, observers on Mars would see Phobos at just one-third the width of the full moon as seen from Earth. Conversely, someone standing on Phobos would see Mars dominating the horizon, enveloping a quarter of the sky.

From the surface of Mars, Phobos can be seen eclipsing the sun. However, it is so tiny that it doesn't completely cover our host star. Transits of Phobos across the sun have been photographed by several Mars-faring spacecraft.

The origin of Phobos and Deimos is still being debated. Scientists concluded that the two moons were made of the same material as asteroids. This composition and their irregular shapes led some astrophysicists to theorize that the Martian moons came from the asteroid belt.

However, because of their stable, nearly circular orbits, other scientists doubt that the moons were born as asteroids. Such orbits are rare for captured objects, which tend to move erratically. An atmosphere could have slowed down Phobos and Deimos and settled them into their current orbits, but the Martian atmosphere is too thin to have circularized the orbits. Also, the moons are not as dense as members of the asteroid belt.

Phobos may be a pile of rubble that is held together by a thin crust. It may have formed as dust and rocks encircling Mars were drawn together by gravity. Or, it may have experienced a more violent birth, where a large body smashing into Mars flung pieces skyward, and those pieces were brought together by gravity. Perhaps an existing was destroyed, reduced to the rubble that would become Phobos.

Hubble took the images of Phobos orbiting the Red Planet on May 12, 2016, when Mars was 50 million miles from Earth. This was just a few days before the planet passed closer to Earth in its orbit than it had in the past 11 years.

Explore further: France, Japan aim to land probe on Mars moon

Related Stories

France, Japan aim to land probe on Mars moon

April 13, 2017

France and Japan want to recover pieces of a Martian Moon and bring them back to Earth, the head of France's National Centre for Space Studies (CNES) said Thursday.

Fantastic Phobos

August 21, 2012

(Phys.org) -- Some 135 years after its discovery, Mars’ largest moon Phobos is seen in fantastic detail – and in 3D – in an image taken by ESA’s Mars Express spacecraft as it passed just 100 km by.

Does Mars have rings? Not right now, but maybe one day

March 20, 2017

As children, we learned about our solar system's planets by certain characteristics—Jupiter is the largest, Saturn has rings, Mercury is closest to the sun. Mars is red, but it's possible that one of our closest neighbors ...

A Martian eclipse, captured by Curiosity

September 18, 2012

Yes, Mars gets eclipses too! This brief animation, made from ten raw subframe images acquired with Curiosity's Mastcam on September 13—the 37th Sol of the mission—show the silhouette of Mars' moon Phobos as it slipped ...

Recommended for you

Neutron-star merger yields new puzzle for astrophysicists

January 18, 2018

The afterglow from the distant neutron-star merger detected last August has continued to brighten - much to the surprise of astrophysicists studying the aftermath of the massive collision that took place about 138 million ...

New technique for finding life on Mars

January 18, 2018

Researchers demonstrate for the first time the potential of existing technology to directly detect and characterize life on Mars and other planets. The study, published in Frontiers in Microbiology, used miniaturized scientific ...

North, east, south, west: The many faces of Abell 1758

January 18, 2018

Resembling a swarm of flickering fireflies, this beautiful galaxy cluster glows intensely in the dark cosmos, accompanied by the myriad bright lights of foreground stars and swirling spiral galaxies. A1758N is a sub-cluster ...

16 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

unrealone1
1 / 5 (4) Jul 20, 2017
But the Hubble cannot see the moon landings?
Solon
1 / 5 (4) Jul 20, 2017
Most likely Hubble is 'seeing' Phobos at non-visible wavelengths, the image info should be available online but usually its a chore locating it.
jonesdave
5 / 5 (5) Jul 21, 2017
But the Hubble cannot see the moon landings?


Why would it need to? They've been seen by other spacecraft.
jonesdave
5 / 5 (1) Jul 21, 2017
Most likely Hubble is 'seeing' Phobos at non-visible wavelengths, the image info should be available online but usually its a chore locating it.


It's visible wavelengths. It'd look very different in IR or UV.
SteveS
5 / 5 (8) Jul 21, 2017
But the Hubble cannot see the moon landings?


This was such a good question that I thought I'd try to find out why. I think it's because Phobos appears over 16 times larger from Hubble than the Apollo lander does.

Mars near opposition is about 100,000,000 km away and Phobos at its smallest is 18 km wide, so ratio of size to distance is about 1.8 times 10 to the minus 7

Moon at its closest is about 362600 km away and the width of the Apollo lander is about 4 m which gives us a ratio of about 1.1 times 10 to the minus 8

18 / 1.1 = 16.36

I will be highly embarrassed if I've misplaced a decimal point here, but I would still appreciate somebody checking my math
RNP
5 / 5 (7) Jul 21, 2017
@SteveS
Your math looks right. However, one *minor* point: Mars was only 80,000,000 km from Earth when the observations were made (see penultimate paragraph of https://www.nasa....d-planet ). So the ratio you calculate comes out more like 20:1
antialias_physorg
5 / 5 (5) Jul 21, 2017
But the Hubble cannot see the moon landings?

Someone else seems to have had the same question (with direct answer as to resolution in arcsecs)
http://hubblesite...mp;id=77
The resolution of Hubble is about an order of magnitude worse than would be needed.

Getting to grips with the scale of things is really where it's at when looking at the universe. Most people already have difficulties handling stuff like area of a nation/continent/ocean (as we never had an evolutionary need to understand such dimensions). When we move to space stuf gets....big really, really fast.

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
-- Douglas Adams (The Hitchhiker's Guide to the Galaxy)

jonesdave
5 / 5 (4) Jul 21, 2017
I assumed the question about Hubble not being able to see evidence of the moon landings, was part of the loony moon landing hoax cult. Apologies if it wasn't. However, with Hubble being mostly a NASA instrument, I doubt the aforementioned loons would accept such evidence. NASA has already published images of moon landing sites taken from LRO. There is other evidence from Japanese, Chinese & Indian spacecraft.
antialias_physorg
5 / 5 (5) Jul 21, 2017
There is other evidence from Japanese, Chinese & Indian spacecraft.

...which the loons won't accept, because it's all a global conspiracy to...erm...do what exactly? That is something they haven't yet made entirely clear.

Hmm...there seems to be a ruinning theme here. Everything they don't understand is a global conspiracy. (Given the sucky track record of any one government keeping ANYTHING under wraps it's really cool how efficient these global conspiracies are, eh?)
Lex Talonis
not rated yet Jul 22, 2017
Hubble was put to death 600 years ago, by the pope, for saying the sun revolved around the earth.
antialias_physorg
5 / 5 (1) Jul 23, 2017
Hubble was put to death 600 years ago, by the pope, for saying the sun revolved around the earth.

Erm...no.
https://de.wikipe...n_Hubble
TechnoCreed
not rated yet Jul 23, 2017
A question to those who posted stupid comments.

Since when do we need to resolve an astronomical object to see it ?
unrealone1
1 / 5 (4) Jul 24, 2017
Where is the moon landing film showing 1/6th Earth gravity, there is none.
Speed up the film of the rover and you get Earth gravity.
Slow down the film and you get moon gravity, it's that easy..
jonesdave
5 / 5 (2) Jul 24, 2017
Where is the moon landing film showing 1/6th Earth gravity, there is none.
Speed up the film of the rover and you get Earth gravity.
Slow down the film and you get moon gravity, it's that easy..


Oh dear. What an idiot. Nothing more needs to be said, Do we all agree?
Lex Talonis
not rated yet Jul 25, 2017
Nooo it's true.... I was in the studio filming the "faked moon landings"......

Lex Talonis
not rated yet Jul 25, 2017
@antialias_physorg

Errrrrrrmmmmm Yes.

And everyone knows that wikipedia is NOT an authorative source of information.

"Hubble was put to death 600 years ago, by the pope, for saying the sun revolved around the earth."

I even have the commemorative limited edition plate celebrating this fakt.

https://s-media-c...tery.jpg

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.