Scroll down to read this post.


I am now running my annual July fund-raising campaign to celebrate the twelfth anniversary of the establishment of Behind the Black. For many reasons, mostly political but partly ethical, I do not use Google, Facebook, Twitter. These companies practice corrupt business policies, while targeting conservative websites for censoring, facts repeatedly confirmed by news stories and by my sense that Facebook has taken action to prevent my readers from recommending Behind the Black to their friends.


Thus, I must have your direct support to keep this webpage alive. Not only does the money pay the bills, it gives me the freedom to speak honestly about science and culture, instead of being forced to write it as others demand.


Please consider donating by giving either a one-time contribution or a regular subscription, as outlined in the tip jar below.


Regular readers can support Behind The Black with a contribution via paypal:

Or with a subscription with regular donations from your Paypal or credit card account:

If Paypal doesn't work for you, you can support Behind The Black directly by sending your donation by check, payable to Robert Zimmerman, to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652


You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above. And if you buy the books through the ebookit links, I get a larger cut and I get it sooner.

The longest lava tube in the solar system?

A lava tube on Mars
Click for full image.

Before I delve into today’s cool image, I think it important to explain to my readers why I seem to post so many cool images from Mars. The simple explanation is that Mars right now is where almost all the cutting edge planetary research is taking place, and as a science journalist focused on space exploration I must go to that cutting edge. My dear readers know that I love variety (just consider the evening pauses on Behind the Black), but you can’t ignore the reporting of real discoveries simply to increase the diversity of one’s posts. This is too often what modern news outlets do, which is also why they often miss the real story.

Anyway, today’s cool image to the right, rotated, cropped, and reduced to post here, shows only a small section of what might be the longest lava tube in the entire solar system. Taken on May 5, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it shows a string of pits along a meandering depression coming down the northwest flank of the giant volcano Arsia Mons. The image was a follow-up to a July 2014 photo of the same location, and was taken to produce a stereo pair.

The feature strongly suggests a lava tube, with the pits being skylights into the meandering underground void. From top to bottom this section of the tube is a little over three miles long. Since there are lava tubes on Earth far longer, this one image hardly makes this the longest tube in the solar system.

The tube, however, extends off the image both at the bottom and at the top. Not many high resolution images have been taken in this area, so it is therefore hard to say how far the tube extends. Other nearby high resolution images in this area however have found similar lava tubes, which conceivably could be part of the same tube. The overview map below shows the relationship.


The blue rectangle indicates the location of the photo above. The overlapping white rectangles numbered one indicate the location of two other lava tube images, each discussed at these posts:

The white box numbered two is another image showing a similar trending depression, though in that case there are no visible skylights. Number three however is another lava tube with skylights, higher up the mountain.

In every image the trend of the tubes or depressions is the same, downhill from the southeast to the northwest. In every image the prevailing winds blow in about the same direction, coming down the mountain’s slope. Excluding #2, which is slightly off line, all the other tubes align nicely and might very well be parts of the same tube.

Finally, the depressions and skylights appear to get larger as you go up the mountain, something entirely to be expected.

With the rim of Arsia Mons about 280 miles away from lava tube #1, and about 40,000 feet higher, this tube has the potential to be many times longer and deeper than the longest and deepest lava tube on Earth, Kazumura Cave in Hawaii, which is just under 41 miles long with a depth of 3,613 feet. And since these giant volcanoes on Mars are by far the largest so far found anywhere in the solar system, this tube could easily be the largest for many light years.

Its underground cross-section could be also be much bigger, due to Mars’ lower gravity. And though there is almost no evidence of shallow ice here near the equator, there still is evidence both of past glacial activity on the slopes of Arsia Mons as well as seasonal water clouds overhead. These lava tubes might therefore still have ice in them, and thus provide a potential future colony site.

Conscious Choice cover

From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


Available everywhere for $3.99 (before discount) at Amazon, Barnes & Noble, and all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.


  • David M. Cook

    Robert, please don‘t apologise for posting these images! Sure, sometimes I scroll past one & say ho-hum, but most are gems! Keep ‘em coming!

  • David M. Cook: That wasn’t meant as an apology, merely an explanation why so many of these images are from Mars.

    Either way, shame on you for thinking ANY of my cool images are “ho-hum!” They are all gems, you simply need to look harder. That is an order! (I’m trying to get with the program of controlling what everyone does. It’s the IN thing, I hear.)

  • Alex Andrite

    Lava tube inhabitants can be harmful to the incoming Pioneers, especially at night.

    Meanwhile, what very cool camp sites lurk there under ?

Readers: the rules for commenting!


No registration is required. I welcome all opinions, even those that strongly criticize my commentary.


However, name-calling and obscenities will not be tolerated. First time offenders who are new to the site will be warned. Second time offenders or first time offenders who have been here awhile will be suspended for a week. After that, I will ban you. Period.


Note also that first time commenters as well as any comment with more than one link will be placed in moderation for my approval. Be patient, I will get to it.

Leave a Reply

Your email address will not be published.