You know that embarrassed feeling you get at dinner parties when one of the guests is making a complete prat of themselves, and everybody knows it but them, and the humane thing to do would be to get them to stop, but you are not your brother’s keeper and, besides, they probably wouldn’t listen to you anyway? That’s the feeling I had going around the Barbican’s excruciating attempt to create a Martian Museum of Terrestrial Art. What a cringe-making display of creative curatorship.

The idea, if that is not too weighty a word for it, was to imagine what a group of Martian anthropologists might find if they came to Earth, or Terra, as it is called in the show, and encountered what we describe as “contemporary art”. Fascinated by our taste for this strange stuff, they decide to collect representative samples and display them in a special museum back home: the Martian Museum of Terrestrial Art. This show.

How did it ever get past the first meeting? If the Martian Museum thing had merely been a metaphor, a way of seeing, then no great harm would have been done and the results might even have been informative. Alas, the Barbican has gone all the way with its expensive pretence. A whole Martian alphabet has been invented for the captions. Lines of spooky copper mapping inserted into the floor guide you through the display in a cod Martian fashion. The main catalogue text - or, rather, the text for the Encyclopaedia of Terrestrial Art - has been written by agent 083TOM33McC5 THY. And the entire event sets out to feel as if it were, indeed, created by Martians.

There is nothing wrong, of course, with displaying a bit of childishness in the conception of an exhibition. Having fun is seen as a perfectly proper artistic ambition for a cultural institution these days. Look at Tate Modern, the Alton Towers of contemporary art. Only a really embittered cultural oldie - like me - would begrudge children the exercise they get jumping backwards and forwards across that famous crack by Doris Salcedo that currently divides the Turbine Hall. Where the Martian Museum pretence goes horribly wrong is in the doing. A deception of this magnitude needs to get the details exactly right to avoid feeling naff. The Barbican’s curators, however, are neither good enough writers to come up with convincing Martian texts, nor good enough designers to create a convincing Martian scenario, nor deep enough thinkers to arrive at convincing Martian conclusions, nor rich enough impresarios to get in a big enough team of FX specialists to pull off something this ambitious. The results are seriously eggy.

Our fake Martian anthropologists have divided human art into four categories: Kinship and Descent; Magic and Belief; Ritual; and Communication. Funny how these sound exactly like the kinds of categories minor earthlings who have been through a curatorship course at a London “polyversity” might have come up with. Kinship turns out to mean “quotation” or “sampling”. And it will not surprise you to learn that the Martian Museum begins its investigation of “contemporary art” with a tribute to the antics of Marcel Duchamp and his followers. One of the reasons Tate Modern’s current examination of the relationship between Duchamp, Man Ray and Picabia is such a fine show is that it presents Duchamp as a genuinely complex and mystical thinker, rather than the infantile pedlar of bad jokes adored by his more stupid contemporary followers. Tate Modern has returned Duchamp’s depth to him. This silly affair takes it away again.

As the whole show is a badly conceived one-liner, most of the art in it appears regrettably shallow. Thus, an audio work by Tacita Dean that takes us on a circuitous drive around Utah’s Great Salt Lake in search of Robert Smithson’s seminal piece of land art, Spiral Jetty, ends its long journey on a short joke. Having driven for hours, the artist finally arrives at her destination and admits: “I’m not sure this is the Spiral Jetty.”

The surrounding artists play it for laughs. Maurizio Cattelan gives us a pretend Picasso welcoming us to a pretend Roy Lichtenstein bedroom. Sherrie Levine has created a version of Duchamp’s notorious urinal, made this time of precious bronze. What we see here is contemporary art’s bottomless interest in itself: not Kinship but Narcissism. Aneta Grzeszykowska has recreated Cindy Sherman’s famous Untitled Film Stills, which were a recreation of classic B-movie moments. Douglas Gordon gives us Self-Portrait as Kurt Cobain, as Andy Warhol, as Myra Hindley, as Marilyn Monroe.

A genuinely insightful Martian anthropologist might conclude from all this giggly evidence that we have become a society addicted to irony, yet petrified of emotion. There are, in fact, plenty of interesting works in the show. In the subsection devoted to Kinship Diagrams, Richard Hamilton presents an intriguing parade of Polaroid portraits of himself, taken by assorted passing pals, from Cartier-Bresson to John and Yoko, from Warhol to Brood-thaers. The Magic and Belief section focuses on art’s habitual urge to achieve impossible transformations, and it was encouraging to see Michael Craig-Martin’s infamous glass of water on a shelf, with its accompanying text insisting it is actually an oak tree, making sense for a change. I had a decent laugh, too, at Dieter Roth’s decision to shred a German book and stuff it into a sausage to create “Literaturwurst”.

Although this jokiness results in some moments of decent artistic amusement, it leads, in the end, to an unacceptable betrayal of art’s seriousness. In the Communication section, a lovely abstract carving by Barbara Hepworth is presented as a portrait of “a Cassiopeian dignitary” encountered by Martians in Greece. That cheap gag belongs in an edition of The Dandy, not in a serious art exhibition. If Hepworth were alive to see her sculpture being thus lampooned she would be appalled. The immense hubris of the curators keeps leading to crass cultural misjudgments. In their urge to smirk and wink, they make it impossible for the profundity of any work in the show to shine through. Fine pieces of sculpture, like James Lee Byars’s gilded marble column, or that chilling self-harming performance by Marina Abramovic, in which she cuts a star onto her own stomach with a broken wineglass, are simply not allowed to feel deep or harrowing or meaningful.

Had this outrageous display of curatorial arrogance told us something important about contemporary art, it might, at a push, have been justified. But the only obvious conclusion reached here - that all contemporary art made by humans needs to be Duchampian in tone - is actually a big lie that tells us everything about these curators and nothing about the rest of us.

Martian Museum of Terrestrial Art, Barbican, EC2, until May 18

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