Leaving Earth cover

In 2019 I obtained from my former publisher the last 30 copies of the now out-of-print hardback of Leaving Earth. I sold about half of these, and with only a handful left in stock I have raised the price. To get your own autographed copy of this rare collector's item please send a $75 check (includes $5 shipping) payable to Robert Zimmerman to

Behind The Black, c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

I will likely raise the price again when only ten books are left, so buy them now at this price while you still can!

Also available as an inexpensive ebook!

Leaving Earth: Space Stations, Rival Superpowers, and the Quest for Interplanetary Travel, can be purchased as an ebook everywhere for only $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from my ebook publisher, ebookit.


Winner of the 2003 Eugene M. Emme Award of the American Astronautical Society.

"Leaving Earth is one of the best and certainly the most comprehensive summary of our drive into space that I have ever read. It will be invaluable to future scholars because it will tell them how the next chapter of human history opened." -- Arthur C. Clarke

Crested Saguaro

Crested saguaro

Today I took the morning off to do a hike with Diane and friend Susan. I did this mostly because other caving-related conservation work on recent and future weekends has made it impossible for me to go hiking with my wife. Since she hikes with Susan on Fridays, I decided to join them.

We went to Tucson Mountain Park, on the west side of Tucson, to do one of the more well known trails. The photo to the right, taken by Diane back in 2016, shows the spectacular crested saguaro she discovered in plain site on that hike but had gone unnoticed by us for years.

Everyone knows saguaros for their classic western look that makes it the state wildflower of Arizona. Normally they have a central post that sometimes has one or more arms extending from it. For normal saguaros the tops of the central post and the arms are almost always symmetrical and rounded.

However, in rare cases (about 1 in 10,000) something strange happens and a saguaro begins to grow wildly at its peak, or even along its entire length. Such freaks are called crested or cristate saguaros, and only about 2,200 have been found throughout the saguaro range in the southwest. When you find one it is always with a sense of triumph and wonder.

We began to look for crested saguaros during hikes around 2015, after a friend had shown us two on a nearby hike that we had done frequently without ever noticing this wonder of nature that was right before our eyes. Thus Diane’s discovery to the right in 2016. Today we went back on that same hike and found it again. It had not changed in any way in the past four years that I could tell when comparing pictures. Regardless, it is one of the wildest crested saguaros I’ve ever seen.

No one really knows why this happens. My theory today, in looking at this one, is that it was on drugs.

Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

Unfortunately, that is exactly where that journey takes him.

The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.

He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit.


  • There’s a rather spectacular crested saguaro along a hiking trail just north of Phoenix, in the Seven Springs area of the Tonto National Forest. I haven’t been there recently, but it was still there at least 4 years ago.


    A more modest one is on display at the trailhead by the McDowell Mountain Sonoran Preserve near Scottsdale. It had been recovered from “poachers”, and replanted there in 2006.


  • Gary

    Fungal or bacterial infections are causes of witches’ broom type of abnormal growth on trees. The Alberta Spruce is an example of such being vegatatively reproduced, although sometimes a branch will revert to normal. I suspect this is the case with the cactus.

  • Foxbat

    They have one of these in the Desert Botanical Garden in Phoenix. I highly recommend a visit there.

  • “My theory today, in looking at this one, is that it was on drugs.”

    Any peyote cacti nearby?

  • wayne

    Sturgill Simpson –
    Turtles All The Way Down

  • Alex Andrite

    I nominate this pic for the “Cool Image Time” Club.

    Thanks Diane for the pic and Mr. Z for the lesson.

  • Edward

    Decades ago, I took an ecology class in which the instructor described the saguaro as technically a tree, meaning that when a desert with many of these plants in it is technically a forest. Imagine that, a desert forest!

    Since then, I have heard that the saguaro is only tree-like, which suggests that these parts of the desert are only forest-like. Not quite as imaginative as my instructor’s description, but fun nonetheless.

  • Lee S

    It certainly looks like a cactus…. The very definition of how we Europeans view the dust bowl of the US… ( Blame bugs bunny and roadrunner!!! )
    Is it actually a cactus?
    I know I could google.it, but I’m sure the insight from asking here will be more informative and entertaining!

  • Lee S: You are exhibiting a level of laziness here that deserves no help, and a lot of derision. I provided links in the post that explains all. You can’t even click on those?

  • Lee S

    Bob…. I am taking a glass of wine, and enjoying the 20 minutes I have between putting my kids to bed, and putting myself to bed. Yes, I am perfectly capable of clicking links, and I do know how to Google, but as I actually said, I was expecting something more fun and personal from the good readership of your blog.
    It is unfortunate that the first response I get is a spot of abuse from your good self.
    My request was made in light humour, perhaps my humour doesn’t come across too well in translation.. it wouldn’t be the first time, but don’t worry… I will research this mildly interesting topic for myself… Heaven forbid I be judged as lazy. ;-)

  • Lee S: I work hard to provide people my sources, which also provide a lot of additional cool information. I thus hope you understand my irritation by your question, when I already provided the answer, in the very post you were commenting on.

    In fact, I provided you a perfect way to fill that break time, with your wine. I hope you use it, and enjoy.

  • Lee S

    Bob….. You know I appreciate the service you provide with this blog, I respect and admire your knowledge and the research you do, to feed us unwashed masses tidbits of information from the last frontier, and although we don’t see eye to eye on politics, (to say the least! :-) ) I return day after day to read, learn, and occasionally comment on the topics you post.
    It was not my intention to wind you up, even tho according to my ex wife I am good at winding anything up apart from the clock.
    I wish you a peaceful evening, and promise to be less needy and more clicky in the future!

  • wayne

    “Road Runner Theme”
    Barbara Cameron
    The Cape Coral Jazz Festival 2013

  • Edward_2

    Robert, Have you ever met Don Lancaster?


  • Edward_2: Yup. Local caver of some note. Gave a talk at a Arizona caving event a few years ago about his work on the hanging canals. And he has been a source of information for me for some of the caves in this area.

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.


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