The Jupiter Collisions by Lachlan Mackinnon Faber & Faber, £8.99

Recently, there were reports that Jupiter had been found to possess eight more moons than previously thought, bringing the tally to 48. Lachlan Mackinnon might feel pleased at this timely information, which neatly confirms the relevance of an old theme he addresses with new energy in his title poem: the chastening sense that human concerns are cut down to size when we realise the magnitude of cosmic events.

The "collisions" are the descent of huge fragments of a disintegrating comet on to the surface of Jupiter, observed by the poet either through a telescope or in a film. He reflects that "Each/ pockmark could have swallowed the earth entire", but also that "Nothing could touch us/ from those forty-five light minutes off." The reticent "us" (or "we") - two lovers, we guess - recur often, as does the knowledge that we are both unaffected by the larger happenings in our universe and cannot influence them.

All we have is the briefest privilege of observing and reflecting. Mackinnon exercises that admirably in this absorbing new collection. Those planetary images might suggest a metaphysical treatment of love and time, in the mode of Donne or Marvell; but Mackinnon comes over as more of a post-romantic with imagist inclinations. Inside many poems lurk small stories of a personal sort, full of rueful and precise details about first love, family and school.

"Staying with Friends" skilfully presents an uneasy childhood experience: "the lawn of marital unhappiness,/ the big house and the ha-ha,/ the scary stabled horse/ I knew would kill me with a kick ... the bewildering/ tall grasses, quarrels, poppies/ and adult silences."

Water is a significant motif throughout: "grey/ musclebound water, vast and meaningless". Affection can be "sudden as rain, strong as rivers". Two poem sequences that work better as imagistic miniatures than coherent structures are titled "Pips in a Watermelon" and "A Water-Buffalo in Guangdong Province". There, in a curious but clever inversion, "hang in the air/ like racked clouds/ stacked millennia" (at the Forbidden City). But from China his mind has already wandered back to France with its "thin grass/ bare poplars/ and water standing/ in sodden fields".

Other places - Oxford, a Scottish valley, Prague - resound with pleasing or ambiguous memories. But the Minnesota mining country, which he does not enjoy, sends him away with a conclusion echoing a poet he in no way resembles, Thom Gunn: "Sometimes/ the one comfort is never standing still". Like Peter Reading, who recorded his loathing for the place in brilliant, scabrous comedy, this poet has been to Marfa in Texas, and at least enjoyed its feature of minimalist sculptures by Donald Judd.

There are two excellent, unusual sonnets (one spoken by a crane) and some moving elegies which include a splendid short celebration of WH Auden, "weird dandy of dishevelment", whom he interviewed when a sixth-former. Only one poem tries to grab the reader by the lapels: "River Psalm", with its conversion of all that water into "a vast chorus that roars in the ears of God". Lachlan Mackinnon's too-rare books show an eye for enthralling particularities. It's too soon to merge them in that kind of invocation.