Martian cave confirmed by HIRISE camera

The Mars Reconnaissance Orbiter discovered several "holes" on Mars in May, that stirred a lot of interest. Here is the close up view of one of them (Jeanne).

A 500-feet... hole?

It's quite obvious that it isn't simply a crater, but what is it then? Is it a caldera filled with extremely dark matter, like the Wau Namus, that appears as a hole in the deserts of Lybia? Is it a lake of oil? Is it caused by sandworms?



The Sun's angle wasn't too low when the image was taken, so the fact that we can't see the walls means it can't really be a pit. The most likely explanation is that it is a sort of skylight, a hole in the ceiling of a cave, that also occur on Earth. If the cave is very deep and large, the illuminated floor can't be seen from exactly above, and we just see a black hole instead.

A skylight (photo by Gus Frederick)



The hole - and 6 others - lie on the slopes of one of the largest volcanoes in the Solar System, Arsia Mons. (More context here, but Arsia Mons is so large it still won't fit on the image). So probably the hole is on the ceiling on a horizontal lavatube.

Infrared measurements also confirmed that they should be caves indeed, as they appear colder than their surrounding during daytime, while warmer in the night.



Here's another feature, from a different region of Mars. This was interpreted as horizontal lavatube, the roof of which collapsed, except for a short section (forming a natural bridge):

A trough in Tartarus Colles, Mars

In the past weeks, the HIRISE team were now able to make another close-up image of Jeanne, with different illumination:

The same feature as the first image. Taken on 8 August.

Here it looks more like a vertical shaft, or just a deep pit. It has a diameter of about 150 meters, and a depth of least 78 meters. Luckily there are chances of peeking even deeper, when the Sun climbs higher on the Martian sky in a few months.

Aurora on Ganymede

So aurorae have been observed on Earth, the gas giants, and even Jupiter's moon Io. And there are even more! In 1972, it was discovered that the largest Jovian moon, Ganymede has a tenuous oxygen atmosphere. Its source is thought to be not plants, as on Earth, but the solar radiation splitting water ice into oxygen and hydrogen (and the latter then escapes into space more easily). Since the visit of the Galileo orbiter, we also know that Ganymede has its own magnetic field (the only satellite known to have one!). So with both an own magnetic field and atmosphere, it's no surprise that Ganymede also has aurorae! The green glow on this picture, on and above this moon, has the same source as the green glow in the polar lights on Earth - transitions of excited oxygen.

You can check out the 17th Carnival of Space blogs.

Space-X update

Merlin engine test

Elon Musk has a long update about the activities of Space-X, and a lot about Falcon-9. And also cool pictures and the above video of a Merlin (1C) engine firing on the test stand. With cool sound!

A mission to Phobos: Fobos-Grunt

Apart from the well known Mars Exploration Rovers, the current Mars Odyssey, Mars Reconnaissance Orbiter, the soon to arrive Phoenix Mars Lander, and ESA's Mars Express, and the various planned future Mars missions (even non-governmental ones, like the Archimedes balloon probe i mentioned earlier, apart from all those, there is also a plan to (re)visit a Martian moon, Phobos.

Russia, after having a lot of bad luck with Mars, planned a double Phobos mission in 1988. One of the two spacecraft did eventually reach Phobos, but then fell silent (the computers went wrong, likely because of insufficient shielding of the electronics). In 1989, money ran out, and all subsequent plans were shelved (except from a failed launch in 1996).

An image of Phobos and Mars, taken by Fobos-2 in 1989

Now it seems that new plans are on the drawing board again, with probably (hopefully) serious political backing. The new Phobos mission is called Фобос-Грунт (Fobos-Grunt, meaning "Phobos Soil"). As the name indicates, the spacecraft is intended to land on this tiny moon, take soil samples, and return the samples to Earth.

More interesting than words and numbers, the following video shows most of the details - it's quite easy to get even if you don't speak russian:


The project seems to be quite ambitious, given they had only one interplanetary probe in the last 18 years (and that was also destroyed after launch). However, if there's a chance that even a part of this mission will come true, it's already good news to any space enthusiast.



And there's more: nowadays Mars seems to be such a magnet for research that China also jumped on the bandwagon, and signed a deal with Russia, that they can include their own micro-probe on Fobos-Grunt. The Yinghuo-1 (萤火一号, named after Mars) spacecraft will be about 100 kg. It's going to be an orbiter with simple capabilities: taking pictures of the planet and making magnetic measurements.The next launch window will be in October 2009, so work should be already in progress, and probably we'll soon get some more infos...

Yinghuo-1

On-orbit and post landing image of space shuttle tile damage

Armadillo's rocket crashed during testing

Another accident at a private space company - no one is hurt, but Armadillo Aerospace' Texel craft is apparently destroyed during a test flight. The New Scientist has the full story.

No pictures have been released, these two videos show Pixel (Texel's twin) at the X Prize Cup in 2006 (which they nearly won):

Bigelow ads to be viewed from space

Hmm, these Bigelow people are really crazy. They put a projector on their orbiter, so that they can project ads on the outside of the craft :-)

Shiveluch - measuring height from shadow

What on Earth is that? This is a satellite image of an erupting volcano. What you can see is the plume from exactly above, before it got smeared by the winds.

Shiveluch volcano is on the Kamchatka peninsula, here are the details of this eruption in last winter, and a larger image.

Can we guess the height of the plume?

Well, we have to find out how high was the Sun (that casts this shadow) on the sky at that moment. The page says Aqua satellite took this picture at 02:00 UTC on March 29. Kamchatka is only about 20 degrees west from the date line (which is about opposite from the 0 meridian, just to appreciate how vast Russia is). The exact latitude and longitude of Shiveluch is 56°63' N, 161°32' E. That means local noon is about 161°/15° = 10.75 hours = 10 hours 45 minutes before noon in Greenwich (the Earth turns 360 degrees in 24 hours, or 15° in one hour). Or to put it another way, it's 10:45 later than the Universal Time. So the local time was 02:00 + 10:45 = 12:45, or 3/4 after noon, when the picture was taken. (Of course this is a perfectly "local time" defined by the apparent movement of the sun - we don't care for time zones that can be arbitrarily defined by authorities). However, we need a correction to this, because Earth's orbit is not a perfect ring, and that results in a slight change of the apparent speed of the Sun's movement on the sky (as for the effects of the eccentricity of Earth's orbit, see the explanation). This correction is never more than 15 minutes though, and on March 29 it is only about 5 minutes (see the explanation). Now let's make a small cheat here. Let's just say it was 12:00 local time, to make things easier. Local noon means the Sun is at its highest elevation (on a given day). The highest elevation depends on the part of the year - it climbs much lower in winter and higher in the summer. But note that March 19 was only 8 days after the spring equinox. So let's just say it was approximately spring equinox (our 2nd cheat). This we prefer because it's easier to tell, how high the Sun climbs. On equinox day, if you stand on the equator (latitude 0°), the Sun passes exactly overhead. If you stand on the North or the South pole (latitude 90°), the Sun circles exactly on the horizon. And if you stand on latitude 56° N, the Sun will appear to move around along a circle in a plane that is tilted by 56 degrees from vertical - or 90°-56°=34° above the horizon. So it reaches its highest elevation on the sky at 34°. So we know that at the time the above photo was taken, the Sun was 34° high on the sky. (actually i think the two cheats i made (it's a bit later in the day, but it's also a few days after equinox) somewhat cancel out each other, so this might be a fairly good approximation, if i didn't do any mistakes of course.) The photo appears to be oriented north (check an atlas or google maps), so the fact that shadows fall almost exactly up/north reassures us that it indeed was pretty close to noon. (Making the above calculations of the local time somewhat unnecessary...)

I measured the length of the shadow (the shadow of the whole big plume) to be 53.4 pixels on average, which equals to a length of 13 km. In the center of this ash cloud is an other shadow, which probably indicates a secondary, smaller plume (if it's possible at all) that rises above the large one, and casts a shadow maybe 6-12 pixels long or 1.5-3 km. Now knowing the sun was 34 degrees high, a simple trigonometry gives us tan(34°)*13 km = 7.8 km (4.9 miles) for the height of the main plume, or probably 8.7-9.6 km for the whole thing.


As you can see on the drawing above, this is the height of the plume compared to the plains around. The height of the volcano itself is about 3 km, so the height of the ash cloud may be a little less. From this image it seems that it's probably surrounded by low lying plains (I tried to check it on google maps but the surroundings of the volcano are clouded there by an other ash cloud!). So maybe it really rises 2-3 km above its surroundings.



Unfortunately i don't know much about eruptions. Is it realistic that 10 minutes after the eruption the plume is at 8-9 km? Probably yes.

This way, one could teach a little physics (or astronomy), armed with only this beautiful photograph. Actually you can go further. Like start thinking about why is the landscape so snowy in late March, when Kamchatka is about as far north as Denmark or Britain?

Phoenix photos

NASA's Phoenix Mars Lander was succesfully launched today . You can see some images of it from its last moments in the cleanroom.

The last picture in the gallery is a little funny. You have to be really careful with accounting all the parts, not to forget something on the spacecraft that doesn't belong there...

Carnival of space

Various posts at the 14th Carnival of Space.


One of them shows, how really easy it is today, to make astrophotos, using a telescope and your mobile phone : Stupid Mobile Phone Tricks.

It's also nice too see the counterparts of Martian blueberries in Utah.

Although research has recently very much shifted away from the Moon, and we're all excited about 1) how exciting Mars is 2) how much more exciting the outer solar system turns out to be than we thought ; it's good that someone shows, that our understanding of the Moon has changed as well, and looks like it also appears more and more interesting.